STEAM BOILER 
ENGINEERING 




JIELIOS 

Y- ^ (^ K fy r • -ir^r^ ^ 



U^ '-—.?' 






HEINE SAFETY 
BOILER COMPANY 



>0^ 



■'^> ,,^' 



#' ^ 



'' ^. 



•^c 









>>, 



■'c. 






t/> ,^\' 



A^" 



-5 •^... 



v-^^ 



'f -^^ 



HELIOS 



CORRECTIONS 

Page 51. line 13 and 14 from bottom. 

For "H. C. Meinholdt" read "H. C. Meinholtz" 

Page 57, line 10 from bottom. 
For "10 lb." read "21/2 lb." 

Page 83. line 6 from bottom. 

Cross out sentence beginning "Its specific heat" 

Page 118, caption. 

For "Sixteen" read "Twenty" 

Page 401, Fig 193 caption, 
or or read and 

Page 607, line 6 from bottom. 

For "Fig. 263" read 'Tig. 264" 

Page 608, line 16 from top. 

For "Fig. 258" read "Fig. 259" 



STEAM BOILER ENGINEERING 

A Treatise on Steam Boilers and 

the Design and Operation 

of Boiler Plants 




Published by 

HEINE SAFETY BOILER CO. 

W hAanufacturers of 

water tube boilers 
Saint Louis, Missouri 

1920 



^2, 



^<^^^'^ 



•^\^ 
^ V^"^ 



TWENTY-SEVENTH EDITION 
COPYRIGHT 1920 

HEINE SAFETY BOILER COMPANY 

SAINT LOUIS, MISSOURI 



It has been decided to follow the usual practice of 
giving new numbers to all new editions and of repeating 
the edition numbers on reprints only. In conformity uith 
this, the previous editions have been renumbered as 
follows: 



Old Dates of New 
Edition Publi- Edition 
Numbers cation Numbers 

1 1893 1 

1 1893 1 

2 1893 2 

2 1893 2 

3 1894 3 

3 1894 3 

4 1895 4 

5 1895 5 

5 1895 5 

6 1896 6 

6 1896 6 

6 1896 6 

7 1897 7 

7 1897 : 

7 1897 7 

8 1899 8 

8 1899 8 

8 1900 9 

8 1900 10 



Old Dates of New 
Edition Publi- Edition 
Numbers cation Numbers 

9 1902 11 

9 1902 11 

9 1902 12 

10 1904 13 

10 1905 14 

10 1906 15 

10 1908 16 

10 1909 17 

10 1910 18 

11 1912 19 

11 1912 20 

11 1914 21 

11 1916 22 

11 1917 23 

11 1918 24 

12 1919 25 

12 1919 26 

Present 

Edition. .1920 27 



Gift 
Publisher 
MAY i iS£1 



ai 



5 



s-^ 









Heine Safety Boiler Co. 

Qeneral Offices 

ST. LOUIS, MO. 

«Ba<:> 

Plants 
St. Louis, Mo. Phoenixville, Pa. 



Branch Offices 



NEW YORK BOSTON PHILADELPHIA 

11 Broadway 50 Congress Street Pennsylvania Bldg. 



PITTSBURGH 
Park Bldg. 



CHICAGO 

First National Bank Bldg. 



CINCINNATI 
Union Trust Bldg. 



NEW ORLEANS 
Godchaux Bldg. 



DETROIT 

Dime Bank Bldg. 



CLEVELAND 

Schofield Bldg. 



DENVER 

Stearns-Roger Mfg. Co. 
1718 California Street 



Representatives 

DALLAS 

Smith & Whitney 
Southwestern Life Bldg. 



HAVANA, CUBA 
Oscar B. Cintas 



SAN FRANCISCO 

Dorward Engineering Co. 

Cunard Bldg. 



CHARLOTTE, N. C. 
Alexander & Garsed 



YOKOHAMA, JAPAN 
Takata & Co. 



TORONTO 
Henry Engineering Co. 




:3 
o 



173 



O 

c 



^m 



-If ^ 

» — i * " 

■a 



OS 



> 
o 



X 






ml 



o 



-3 




C 



CO 

X 



C 



(L) 



o 



03 



CO 

c 

CO 

■i-l 
CO 

(U 

.S 
'C 



Preface to 
Twenty-seventh Edition 

THE present edition of Helios is entirely new. 
Since the book was first published, almost 
twenty-seven years ago, steam engineering 
practice has been completely revolutionized. 
Our knowledge of fuels, of their proper combus- 
tion, and of steam-power applications has been 
developed to a remarkable extent. 

This new Helios is intended to summarize the 
latest commercial developments in boiler-plant 
practice. It was written, compiled and edited 
by the Research Department of the Heine Safety 
Boiler Co. for the large number of engineers and 
men with engineering interests who have to deal 
with problems of boiler plant design and instal- 
lation. 

The preface to the first edition of Helios, which 
appeared in July, 1893, was written by Col. 
E. D. Meier, founder and first president of the 
Heine Safety Boiler Co. This preface, which is 
reprinted on the next two pages, carries a 
message that is as true today as when it was 
written by Colonel Meier. 

Helios — a Text Book on Steam Boiler Engi- 
neering — is respectfully dedicated to all those 
interested in increasing the efficiency, economy 
and capacity of steam power-plants. 

Heine Safety Boiler Co. 

St. Louis, December 11, 1920. 



10 



HELIOS 

Source of All Poiuer I Fountain of Light and Warvrith I 

Adored by the ancient husbandman as the God who blessed his labors 
with a harvest of golden grain ; revered by the early sage as the great visible 
means of the divine creative force ; pictured b}' the inspired artist as the tire- 
less charioteer who drives his four fiery steeds daily across the heavens, his 
head circled by a crowd of rays, his chariot wheel the disk of the sun itself. 

When primeval man began to think, the sun seemed to him the cause of 
all those wonders in nature which ministered to his simple wants, or taught 
his soul to hope. His crude feelings of awe and gratitude blossomed into 
worship, and we find the sun as central figure in all early religions. He was 
the Suraya of the Hindoos, the Baal of the Phoenicians, the Odin of the 
Norsemen, and his temples arose alike in ancient Mexico and Peru. As Mithras 
of the Parsees, he was adored as the symbol of the Supreme Deity, his mes- 
senger and agent for all good. As Osiris he received the worship and 
offerings of the Egyptians, whose priests, early adepts in the rudiments of 
science, saw in him the cause of the annual fructifying overflow of the Nile. 

Modern knowledge, with its vast array of facts and figures, can but verify 
and seal the faith of these ancient observers. What they dimly discerned as 
probable is now the central fact of physical science. From him are derived 
all the forces of nature which have been j-oked into the service of man. All 
animal and plant life draws its daily sustenance from the warmth and light of 
the sun, and it is but his transmuted energv^ we expend, when, with muscle 
of man or horse, we load our truck or roll it along the highway. 

Do we irrigate the soil from the pumps of a myriad of windmills? His 
rays, on plains far inland, supply the energy for the breeze which turns their 
vanes. Does a lumbering wheel drive a dozen stamps and a primitive arastra 
in some Alexican canj-on? Do might}" turbines whirl a million flying spindles 
and shake thousands of clattering looms on the banks of some Xew England 
stream? From the bosom of the ocean and the swamps of the tropics, Helios 
lifted those vapory Titans whose lifeblood courses in the mountain torrent and 
the river of the plain. Do a hundred cars rattle up the steep streets of the 
smiling city b}- the Golden Gate? Are massive ingots of steel forged to shape 
and size by the giant hammers of Bethlehem? The fuel which gives them mo- 
tion was stored for us, ages before man was evolved, by the rays which flash 
from his chariot wheels ! "The heat now radiating from our fire places has at 
some time previously been transmitted to the earth from the sun. If it be 
wood that we are burning, then we are using the sunbeams that have shone on 
the earth within a few decades. If it be coal, then we are transforming to 
heat the solar energy which arrived at the earth millions of years ago." 

Professor Langley remarks that "the great coal fields of Pennsylvania 
contain enough of the precious mineral to supply the wants of the United 
States for a thousand years. If all that tremendous accumulation of fuel 
were to be extracted and burned in one vast conflagration, the total quantity 



11 



of heat that would be produced would, no doubt, be stupendous, and yet," says 
this authority, who has taught us so much about the sun, "all the heat de- 
veloped by that terrific coal fire would not be equal to that which the sun 
pours forth in the thousandth part of each single second." 

The almost limitless stores of petroleum which are found in America and 
in Asia, and the smaller, though still vast supplies of natural gas which some 
favored localities are now exploiting, represent but so much sun-energy trans- 
muted through forests of prehistoric vegetation. 

Another authority tells us that the total amount of living force "which 
the sun pours out yearly upon every acre of the earth's surface, chiefly in the 
form of heat, is 800,000 horse-power." And he estimates that a flourishing crop 
utilizes only four-tenths of one per cent of this power. 

Remembering, then, that this sun-energy reaches us only one-half of each 
day, we ma}^ ivliencver ive learn hoiv, pick up on every acre an average of 175 
horse-power during each hour of daylight, as a surplus which nature does not 
require for her work of food production. 

Attempts to utilize this daily waste have been made, and future inventors 
may fire their boilers directly with the radiant heat of the sun. But whether 
we depend on what he garnered for us ages ago, or quite recently, or on the 
stores he will lavish on us in the future, it is clear that man's continued 
existence on earth is directly dependent on HELIOS. 

In olden times the various trades or guilds chose as their patron saint 
some prominent person who was thought to have embodied in his life-work 
the special means and methods of their craft. By that token we claim Helios 
as our own. He has always carried the record for evaporative efficiency. He 
provides both the fuel and the water for our boilers. He teaches us perfect 
circulation, upward as mingled vapor and water by the action of heat, and 
down again by gravity as rain and river in solid water. It is therefore fit 
that the boiler in which this perfect and unobstructed circulation is made the 
leading feature of construction should have HELIOS as its emblem. 

In the following pages we have some account of the fuels used in the 
practical arts, of the water which becomes the vehicle for transmitting their 
energy into mechanical power, and of the limitations imposed by their varying 
conditions. These must all be taken into account in estimating how much we 
may expect of certain combinations of machinery. 

We trust that the tables and data may be found convenient for ready ref- 
erence alike by professional men, by manufacturers, and by that growing class 
of practical steam engineers who realize that true theory, consonant with 
collective experience, is within the reach of every thoughtful man who pulls 
the throttle. 

E. D. MEIER. 

This explanation of the choice of the word HELIOS, as the name of this 
book, appeared as the preface of the first edition in July, 1893, and the word 
has ever since been a prominent feature of our trade mark. 



12 



CONTENTS 



Preface 9 

Helios, by E. D. Meier 10 

ChaD. 1. Heine Practice 15 



:: rir.g Facilities Operation of Heine Boilers 
: :' r r Characteristics Adaptability 
service Installation 

iinal Drum Boilers Facilities for Cleaning 



Superheaters 
Cross Dm:: Fii.ers 
Marine Boilers 
Standard Specifications 



Chap. 2, Boiler Rating and Design 

Boiler Horsepower Heating Surface Ratios 

Heating Surface Gas Passages 

Grate Surface Baffling 

Chap. 3. Superheaters 



00 



Capacin- and Economy 
Water Circulation 
Steadiness of Water Level 

69 



-"\ r ^ 1 . 

Stea: 



..ll-i Hl.iill.c; 



Limit of Superiteat 
Control ci Superheat 
Types oi St:p err. eaters 



Superheating Surface 
Superheater ^Materials 
Industrial Uses 



Chap. 4, Furnaces and Settings 



-^ ~^^; 



Lias: 



Powdered Coal 
Oil Burning 
Tar Burning 
Gas Burning 
Refuse Burning 



Waste Heat 

Marine Settings 

Refractor}- Materials 

Firebrick 

Radiation and Leakage 



Chap. 5, Mechanical Stokers 

Overfeed Underfeed 



159 



Chain Grate 



Chap. 6, Chimneys and Flues 173 



^izes ::•' -.rrsepower 
r raft ana Capacity- 
Draft Required for Co^l 
Sizes bv Gas 
Oil, Gas and \Vood 

Chap. 7, Mechanica. 

Forced Draft 
Fan Drives 
Operating Difficulties 



Evase Chimneys 
Chimneys at Altitudes 
Chimney Construction 
Self- Supporting Steel 
Guyed Steel 

^raft 

."-m Characteristics 

iting Fans 
Pitot Tube 



Radial Brick 
Reinforced Concrete 
Remodeling 
Breech ings 
Dampers 



223 



Ducts and Dampers 
Induced Draft 
Stack Connections 



Chap. 8, Piping and Accessories 

V. ater Hantnter Weight of Pipe 

Fipin^ S: stents Bursting Pressure 

I lent in cation by Color Pipe Fittings 

iNI ate rials Ranges 

Temperature and Strength Valves 

Standard Pipe Sizes Blow-off Piping 



243 



Steam Pipe Smes 
Water Pipe Sizes 
£^q>ansion and Contraction 
Pipe Anchors 
Expansion Joints 
Steam Separators 



Chap. 9. Auxiliaries 297 



^team rumps 
Centrifugal Feed Pumps 
Power Pumps 
Automatic Regulation 



Feed Water Regulator: 

Injectors 

Feed Water Heating 

Open Feed Heaters 



Qosed Feed Heaters 
Economizers 
Air Heaters 
Engines and Turbines 



13 



CONTENTS 



Chap. 10, Heat Insulation 347 



Surface Resistance 
Bare Surface Heat Loss 



"85 per cent Magnesia" 
Diatomaceous Earth 



Conductivities of Materials Heat Transmission 



Insulation Materials 
Asbestos 



Thickness of Insulation 
Economy of Insulation 



Boiler Drums 
Boiler Walls 
Outdoor Pipe Lines 
Underground Lines 
Cold Water Lines 



Chap. 11, Heat and Combustion 

Theory of Heat 
Thermometry 
Absolute Temperature 
Thermodynamic Scale 
Thermometers 



369 



Chap. 12, Steam 

Entropy 
Expansion 
Saturated Vapors 



Pyrometers Combustion 

Heat Units Ignition Temperatures 

Specific Heat of Solids Air for Combustion 

Heat Transfer Properties of Gases 

Temperature Drop, Boilers Specific Heat of Gases 

407 

Steam Flow, Nozzles 
Saturated Steam Tables 
Superheated Steam Tables 



Superheated Vapors 
Peabody Diagram 
Mollier Diagram 



Chap. 13, Fuel 

Classification of Coals 
Location of Coal Deposits 
Composition of U.S. Coals 
Commercial Sizes 
Sampling Coal 
Analyzing Coal 
Heat Value of Coal 
Mahler Coal Calorimeter 

Chap. 14, Feed Water 

Impurities in Water 
Analysis of Water 
Hardness Test 
Alkalinity Test 
Causticity Test 

Chap. 15, Boiler Testing. 

Personnel 

Duration 

Simple Test Data 

Weighing Feed Water 

Weighing Coal 

Quality of Steam 

Chap. 16, Operation. _. 

Boiler Fittings 

Hand Firing 

Cleaning Fires 

Firing Tools 

Banked Fires 

Quick Steaming from Bank 

Load Signals 

Smoke and Cinders 

Carbon Dioxide 



Ash 

Clinker 

Storage of Coal 

Deterioration in Storage 

Spontaneous Combustion 

Briquets 

Coke 

Tan Bark 



435 

Bagasse 

Liquid Fuels 

Tar 

Colloidal Fuel 

Gaseous Fuels 

Junker Gas Calorimeter 

High and Low Heat Values 

Specifications 

499 



Concentration Test 
Mechanical Treatment 
Thermal Treatment 
Chemical Treatment 
Zeolite Process 



Starting and Stopping 
Simple Test Report 
Simple Test Calculations 
Complete Test Data 
Flue Gas Analysis 
Complete Test Report 



Boiler Compounds 

Priming 

Foa i^ r 

Co on 

Sc 

. 513 

jmplete Test Calculations 
Heat Balance 
Efficiency 
Accuracy 

Steam Used by Auxiliaries 
Liquid and Gaseous Fuels 

551 



Carbon Monoxide 
CO2 Recorders 
Draft Regulation 
Economical Operation 
Control Boards 
Measuring Water 
Metering Steam 
Weighing Coal 
Handling Coal 



Storing Coal 
Submerged Storage 
Conveyors 
Handling Oil Fuel 
Cleaning Boilers 
Renewing Tubes 
Care of Idle Boilers 
Boiler Inspection 
Steam Cost Accounts 



14 




Heine Standard Two Pass Boiler with Setting for Hand Firing. 



15 



CHAPTER 1 



HEINE PRACTICE 

THE first Heine Boiler was designed by Colonel E. D. Meier and 
built in St. Louis in 1882. It is still in first-class working order, 
and is open to public inspection at the St. Louis Plant of the 
Heine Safety Boiler Company. 

Colonel Meier founded the Heine Safety Boiler Company in 
1884 and was president of the company until his death in 1914. 
Heine Boilers have been built without interruption since the com- 
pany was founded ; the fact that many of those sold in the 'eighties 
are still in operation, testifies to the superiority that has always 
characterized them. 

This long period of operation, in conjunction with up-to-date 
factory methods and equipment, has enabled the Heine Company 
to build up an organization of experts in boiler design, manufacture, 
and operation. 

There are two plants — St. Louis, Mo., and Phoenixville, Pa. 
Each plant has complete manufacturing facilities, and consequently 
is an entirely independent source of supply. The general offices of 
the company are at St. Louis. 

Heine Boilers are of two general classes, longitudinal and cross 
drum. While the longitudinal drum type is the standard for land 
service, many Heine users prefer the cross drum on account of the 
low head room required. They are built in both types for marine 
service, though the cross drum is general practice for this work and 
the recognized standard. 

All Heine Boilers for land service are built to conform to 
the requirements of the Boiler Code formulated by the American 
Society of Mechanical Engineers, notwithstanding that weaker (and 
cheaper) construction is permitted in many states. In this code 
are incorporated the most rigid requirements for boiler construction 
and materials. 

Heine Boilers for marine service are built in accordance with 
the rules and regulations of the United States Board of Supervising 
Inspectors. They are approved by Lloyds' Register of Shipping and 
by the American Bureau of Shipping. 



16 




o 

■*-> 

c 

CO 
V 

C 



g 

CO 

a; 

■4-> 

CO 

< 
> 

o 
o 

o 



H E T N K P R A C T T C E 17 

Heine Manufacturing Facilities 

THE two large plants owned and operated by the Heine Safety 
Boiler Company are shown on pages 6 and 7. Both are fully 
equipped with electric, hydraulic and pneumatic machinery, as well 
as with powerful cranes and hoists for handling the heavy weights 
involved in the manufacture of boilers. 

Steam is generated at each plant by a battery of Heine Boilers. 
At each plant the powder equipment — steam turbines, generators, 
condenser and cooling tower, engines, hydraulic pumps and 
accumulators, air-compressors — is installed almost entirely in dupli- 
cate, every precaution being taken to avoid a shutdown. Parts of 
the turbine-room and of the engine and pump rooms of the St. Louis 
plant are shown on pages 16 and 18. The power plant at Phoenix- 
ville is similar to that at St. Louis. 

The boiler-making tools found in the Heine plants include 
rolling and bending machines, flanging and forging presses, 
hydraulic riveters, punches, shears, steam hammers and forges, 
heating and annealing furnaces, for various purposes. Lathes, drill 
presses, boring mills, and other machine tools are used. Special 
machines and equipment, designed and built by the Heine Company, 
are employed for various purposes such as for accurately reaming 
rivet and tube holes. The larger electrically driven machines have 
individual motors, while the smaller machine-tools are belted to 
motor-driven line-shafts. 

Page 20 shows a heavy flanging press and one of the large steam 
hammers in the St. Louis plant. Portable hydraulic riveters are used 
for some operations, such as riveting waterlegs to the drums, 
shown on page 24. Hydraulic "bull"' riveters, page 26, are installed 
in towers equipped with high overhead cranes for handling boiler 
drums and other long parts. Page 22 shows part of the machine 
shop at Phoenixville. Page 30 shows the testing floor at St. Louis. 
In the sheet iron department, parts not subjected to pressure are 
fabricated, such as internal mud drums, deflection plates, boiler 
fronts and breechings. 

Ten Characteristics of Heine Boilers 

CERTAIN features of design and construction insure continuous, 
satisfactory service from all types of Heine Boilers. They can 
be summarized as follows : 

1. Workmanship. Heine Boilers are built by expert workmen, 
in modern shops equipped particularly for the production of high- 
class water-tube boilers. The materials and the construction of 
every Heine Boiler conforms with the rules and regulations issued 
by the highest authorities. This means that Heine Boilers comply 
with the best standards as regards safety, economy and durability. 



18 




o 

c 

e 

o 
o 

G 

"So 

w 



PIEINEPRACTICE 19 

2. Strength. The construction of the waterlegs or headers, 
flanged plates with ample staybolts, is approved and widely accepted 
practice. It has given the greatest satisfaction under such severe 
service as in the locomotive boiler and the Scotch marine boiler, 
and is highly commended by the foremost boiler authorities of all 
countries. It avoids welding, and permits better general design and 
accessibility, closer tube spacing, easier, freer circulation and less 
punishment of material during construction than do any of its sub- 
stitutes. The unusual strength of structure obtained by the direct 
connection of the drum and headers, virtually makes the Heine a 
''one-piece" boiler, well qualified for prolonged hard service. The 
first Heine boiler built was used continuously for 35 years, after 
which period an inspection by The Fidelity and Casualty Company 
showed that it was still in proper working condition. 

3. Overload Capacity. Heine Boilers are adapted for operation 
at high overloads, because of the unusual provision for rapid 
circulation, the large combustion space and the method of baffling. 

4'. Water Purification. In the Heine Boilers a large proportion 
of the scale-forming impurities in the feed-water are deposited in 
the internal mud drum, and are thus prevented from accumulating 
on the heating surfaces. The ordinary mud drum is simply a recep- 
tacle for the collection by gravity (even this is hindered by the 
water circulation) of impurities precipitated within the boiler. 
With the Heine internal mud drum the new feed- water must be at 
least partly purified before it enters the water circulating in 
the boiler. The solids deposited are not hardened by heat, but 
remain in the form of a sludge, which can be easily blown oft'. 

5. Free Circulation and Dry Steam. These are attained in the 
standard Heine Boiler by the use of spacious headers at each end 
of the tube nest, which are connected to the drum by large throat 
passages. The generated steam has ample room to escape without 
pulling water along. In the cross drum boiler, free steaming ability 
is promoted by a device in the upper part of the rear box header, 
which effects a primary separation of the steam and water. The 
return water circulation is along the upper tubes of the main bank 
The steam passes along the horizontal tubes and the final separation 
takes place in the cross drum. 

6. Tube Design. Straight tubes, as used in the Heine Boiler, 
are the easiest to clean, install, examine, and renew ; they give max- 
imum efficiency and the best circulation. 

7. Heating Surface. The gases flow parallel with the tubes in 
the Heine Boiler. After entering the nest of tubes, they do not 
leave it until they are discharged to the breeching. This method of 
gas passage has been proved to give the highest rate of heat trans- 
mission with the least draft loss. 



HEINE PRACTICE 



21 



8. Combustion Chamber. This is of ample size so that the 
gases are thoroughly mixed and burned before they strike the cool 
heating surface. The lower baffhng forms the roof of a reverbera- 
tory chamber, providing ideal conditions for perfect combustion. 

9. Floor Space. The compact arrangement of heating surface 
due to the close tube spacing, lessens the floor space and head room 
required. Any number of Heine Boilers can be set in a single 
battery ; alleyways are unnecessary, so that the saving of space is 
large. Boilers set in a solid battery are immune from most of the 
losses by air infiltration and radiation. 

10. Cleaning Facilities The outsides of the tubes are cleaned 
quickly and thoroughly by a soot blowing system operated from the 
front and back, and provided with every boiler. Side-wall dusting- 
doors are unnecessary, and their absence greatly reduces the air in- 
leakage, insuring a high percentage of CO2 with consequent fuel 
economy. Since straight tubes only are used, the inside surfaces 
are easily inspected and cleaned through the handholes in the water- 
legs. In the cross drum boiler, the tubes and nipples connectuig 
the drum with the box headers are quickly cleaned through the 
manholes provided. 




Section of Drum and Waterleg of Heine Standard Boiler. 
Note the Large Throat Area. 




o 

4-1 

c 
a 



a 
o 

CO 

a; 
C 

'Xi 
u 

CO 



H E I N E P R A C T r C E 23 

Heine Service 

THE Heine Safety Boiler Company maintains an Engineering De- 
partment for the assistance of its clients in the arrangement and 
improvement of new and existing boiler plants. Experience in the 
installation of boilers in plants of widely diversified size and type, 
qualifies us to recommend the best method of procedure to meet the 
conditions prevalent in any particular plant. This service covers 
not only boiler and furnace design for the various types of fuel and 
operating conditions, but includes recommendations as to building 
design, coal and ash handling equipment, piping, stacks, breech- 
ings, etc. 

The Research Department, besides being engaged upon new de- 
velopments in boiler engineering, is constantly rendering assistance 
in such problems as the efficient handling and combustion of all 
kinds of staple and refuse fuels, special furnace and boiler settings, 
baffling to meet unusual conditions, recovery of heat from waste 
gases, chimneys, draft, etc. 

The Library contains a copy of almost every domestic and 
foreign work on power plant engineering, besides a large collection 
of references on every conceivable phase of boiler practice. This 
information is at the disposal of our clients. 

The continuous satisfactory performance of every Heine boiler 
is our vital concern as well as that of the customer. Our interest in 
the boiler does not cease when it has left our shop. A Trouble De- 
partment is maintained, composed of technically and practically 
trained engineers whose principal duties are to assist our clients in 
overcoming any difficulties which may occur in boiler operation. 
This service includes such investigations as the study of firing 
methods, scale formation or priming due to poor water conditions, 
boiler inspection, boiler testing, etc., etc. 

There are sixteen branch offices and three distributing ware- 
houses for repair parts. The production of parts in large quantities 
by modern manufacturing methods, the storage of patterns, etc., 
results in the supply of renewals at small cost; and an eft'icient system 
of records of every ETeine boiler since the first, insures prompt 
shipment. 

Standard Longitudinal Drum Boilers 

THE standard ITeine Boiler, shown on pages 8 and 14, consists of 
a cylindrical shell or drum to which box-shaped headers (water- 
legs) are riveted at each end. These waterlegs are connected by the 
main nest of tubes. 




t 



Jifr - iH ^ 41^ ~~4P -' 
C? €> CI ^i^ 





> 



as 

u 
>> 



(S 

U 

O 



CO 



c 



> 
(2 



HEINE PRACTICE 25 

The drum consists of three sheets, riveted in accordance with 
the approved rules. It varies in diameter from 30 to 48 in. and 
in length from about 17 to 22 ft., according to the horsepower 
required. The longitudinal seams are of the double-strap butt-joint 
type, while girth or circumferential seams are of the lap-joint type, 
single or double riveted. The design of the riveting depends upon 
the pressure to be carried. 

The heads are dished to a radius equal to the diameter of the 
shell, and thus require no internal staying. A flanged manhole, pro- 
vided with a pressed steel cover, forms part of the rear head. The 
main steam outlet and the safety valve are attached to pressed steel 
saddles, riveted to the top of the drum near its front end. 

The material for both waterlegs and drums is the best firebox 
steel plate, made especially to Heine specifications and tested before 
shipment. 




Hollow Staybolts of Heavy Gauge Steel Tubing. 

The waterlegs are connected to the bottom of the drum near each 
end by a throat opening, page 21, braced by forged steel throat stays, 
page 46, which are riveted across when the waterlegs are attached. 
The waterlegs consist of two plates — the tube sheet and the hand- 
liole sheet. These plates are machine-flanged and are joined by a 
narrow plate similar to a butt-strap. The waterlegs are stayed by 
hollow staybolts made of carefully tested mild steel tubing ; these 
are screwed into tapped holes in the two plates, and the projecting 
ends upset from the outside. The tube holes and handholes are 
located accurately and bored to exact diameters. The waterlegs 
are built complete and then hydraulically riveted over the throat 
openings. 

The handholes are round, except a few at the top and bottom, 
which are oval and are used for the introduction of the round plates 
into the waterlegs. The handholes are closed in three different 
ways ; by strong cast iron plates ; by drop-forged steel plates ; or 
by the Key pressed steel handhole caps. All of these are inserted 
from the inside so that the steam pressure tends to tighten them, 
and does not loosen them as in the case of plates applied from 




o 



CO 



u 

CO 

C/3 



m 

C 

•4-< 

a; 
> 

u 
O 

«4-l 



(U 

> 



3 
08 
u 

>> 

u 
CO 



(U 

a 
a 

"5 
cr 

(U 
V-i 

o 
H 



13 



HEINE PRACTICE 



27 



the outside. The plates are held in position by bolts and yokes, the 
latter bearing against the outside of the handhole sheet. Gaskets are 
required with the plates, but not with the Key caps which are rolled 
in slightly tapered holes so that the pressureVithin the boiler tends 
to hold them more tightly. 

Lap-welded steel tubes are supplied with the Heine Boiler, but 
charcoal iron or seamless steel tubes can be supplied as optional 
equipment. The tubes extend between the two waterlegs, and are 





(b) 






Handhole Closures, (a) Cast Iron; (b) Drop Forged Steel; 
(c) Key Pressed Steel Handhole Caps. 



expanded into the tube sheet by roller expanders. The tube ends 
are slightly flared to increase the holding power. 

The baffling on Heine boilers is varied somewhat according to 
the conditions of operation. Page 8 shows the single-pass, and 
page 12 the two-pass system. The simplest arrangement is to place 
the baffle tile on the lowest row of tubes, and a second baffle on 
the second row of tubes from the top, giving a single pass of the 
gases through the tube nest. The lower baffle may be placed on the 
third row of tubes from the bottom, thus giving a partial pass 
through the three lower rows, and a complete pass through the 
remainder of the nest of tubes. In still another arrangement one 
baffle is placed on either the first or third row of tubes from the 




m 



HEINEPRACTICE 29 

bottom, and another baffle introduced a little more than half-way 
up the height of the tube nest, thus giving the products of combus- 
tion two full passes through the nest of tubes. 

The baffle tiles are designed to rest on or between the tube 
rows. The bottom row is formed of specially shaped fire-clay tile, 
while the upper and middle rows are either fire-clay or cast iron 
shapes, according to conditions. 

Heine Superheaters 

THE standard Heine Superheater, page 34, is placed at the side 
of the drum toward the front. It may be single — on one side, 
or in two parts — one on each side of the boiler. One or two units 
are used, according to the capacity and degree of superheat required. 

The superheater consists of a header box divided horizontally 
into three compartments, and with U-tubes inserted into one side 
and bridging the partitions. Steam from the boiler enters the lower 
compartment, passes through the lower nest of tubes into the middle 
compartment, then through the upper nest of tubes into the upper 
compartment, from which it issues. These passages effect a thor- 
ough mixture of the steam and ensure a uniform temperature. 

A small flue built in the side-wall carries part of the hot gases 
direct from the furnace into the rear of the superheater chamber. 
After making a first upward pass over the outermost ends of the 
tubes, the gases make a second downward pass over the rest of the 
tube surface ; and after leaving the superheater chamber pass along 
the boiler drum, thus giving up the remainder of their available heat. 

The header box is built with one seam and one row of rivets, 
the caulking edge being to the front. The two sheets of the box are 
braced by hollow staybolts. Access to the interior is gained by 
handholes closed by inside plates, which are placed opposite the 
tubes. The U tubes are Ij/^-in. diameter, of seamless steel. 

The superheater chamber is of brickwork, with a firebrick roof 
carried by T-bars. The front of the superheater is closed in by 
doors, which prevent radiation and give access to the header box. 

A damper in the outlet of the superheater chamber controls the 
flow of gases ; there is no danger of its becoming overheated, since 
the gases do not come in contact with it until they have been cooled 
by passing through the superheater. The damper is regulated by 
hand from the front of the boiler, or an automatic thermostatic 
control regulates the superheat to within 5 deg. above and below 
the temperature desired. A full and illustrated explanation of the 
temperature control, as well as a discussion of the dangers result- 
ing from uncontrolled and excessive superheats, is given in "Super- 
heater Logic," which also contains a complete description of the 
construction of the superheater. This Heine publication is mailed 
on request. 




o 

2; 



c 

CO 



c 



H 

C 
ca 

C 

o 
u 



HEINE PRACTICE 31 

No scale is deposited in the tubes because flooding of Heine 
superheaters is unnecessary. Closing the damper isolates the tubes 
from the hot gases, and then only saturated steam is delivered. 

The superheater is built complete and tested before shipment, so 
that it is ready for erection upon arrival. 

The arrangement is such that it can be cleaned easily and thor- 
oughly while in operation, insuring efficiency, close temperature 
regulation, and economy. The tubes are smooth and therefore accu- 
mulate very little soot ; this is easily removed by a steam lance 
passed through the hollow staybolts, or by a permanent soot blower 
similar to that on the boiler. 

Adaptability of Heine Boilers 

HEINE Boilers suit the conditions and plans of any power plant. 
There are no doors in the sidewalls and no aisles are required 
between boilers, because all cleaning, inspection and tube renewals 
are done from the front and back. Consequently, any number of 
boilers may be set in single battery and this materially reduces the 
cost of brickwork. With center-retort and side-feed stokers, 
hand firing, oil or gas firing, the space required is greatly reduced 
as is seen by comparing with layouts of other standard boilers ; and 
this lowers the cost of the boiler house. Such plants are generally 
simplified as there are no aisles to bridge, and this also applies to 
piping arrangements Operating efficiency is noticeably increased 
owing to the shorter flues, elimination of sidewall radiation and 
infiltration of air, and avoidance of air-leakage through sidewall 
cleaning and dusting doors and the numerous cracks inevitably 
starting from them. 

Heine boilers are running satisfactorily with stokers and mechan- 
ical furnaces of every standard type. All kinds of fuel are being 
successfully burned under them — fuel oil, gas, pulverized coal, tan 
bark, bagasse and sawdust. They are giving excellent service under 
the most varied conditions of power production, manufacture and 
process, where steam is required either steadily or in heavy and 
irregular drafts. 

The unusual adaptability of Heine Boilers for the utilization of 
waste heat from kilns, stills, metallurgical furnaces and other pro- 
cesses is discussed in Chapter 4. 

Installation of Heine Boilers 

HEINE Boilers of 500 H.P. or less are shipped completely assem- 
bled, page 36, while the larger sizes are knocked down for 
shipment, page 38. For export, they are shipped in separate parcels, 
containing the tubes, the central part of the drum, and the waterlegs 
with short section of drum attached. The cross drum boilers can 
be shipped entirely knocked down, page 40, the headers and drum 




o 

G 

a 






o 
CO 

■M 

(/3 



> 

o 

bO 
•i-i 

> 



HEINEPRACTICE 33 

being complete in all respects so that assembling consists only of 
expanding the tubes. 

When set up ready for service, the Heine Boiler inclines upward 
from rear to front at a slope of one in twelve. The front end of the 
boiler is carried by heavy cast iron columns. For hand-firing, the 
waterleg rests directly on the columns ; while for stoker firing, 
brackets riveted to the waterlegs are supported on the columns, or 
the front of the boiler is carried on an overhead support. The rear 
end rests on rollers bearing on iron plates which are set in the top 
of the low brick wall forming part of the setting. These rollers 
permit expansion and contraction and avoid injurious strains. 

On each side of the boiler is a solid brick wall lined with fire- 
brick and carried to the height of the ornamental front. Returns 
are made at both front and rear, following the curvature of the 
drum and waterlegs, the weight of the brickwork being carried 
by metal supports. The space between these supports and the boiler 
is filled with asbestos fiber, w^hich prevents the ingress of air. The 
space prevents any displacement of brickwork due to expansion and 
contraction of the boiler, since the walls are supported independently 
and slightly away from the boiler. The brickwork is tied together 
by longitudinal and transverse anchor bolts secured at each end of 
the setting and at several places on the sides to substantial rolled 
steel buckstays. The top of the setting is closed on each side of the 
drum by cast iron plates, which rest on the sidewalls and on a tile- 
bar carried by brackets attached to the drum. Openings are left 
at the rear for the exit of the gases. A brick arch is built over 
*he drum to prevent radiation, and is of firebrick in the uptake. 

Over the uptake openings, and supported by the boiler walls, is 
placed a breeching hood of suitable shape to connect with the 
breeching. 

The cast iron fire fronts carrying the fire and ash door frames 
are bolted to the supporting columns, and a substantial firebrick w^all 
is built inside to prevent overheating. The fire fronts support the 
upper ornamental front, page 42. Large doors are provided at both 
front and back for access to the w^aterlegs. 

Stationary grates are ordinarily furnished, but shaking grates or 
any other form of furnace or stoker can be substituted. Stokers are 
frequently set directly under Heine Boilers owing to the large com- 
bustion space, and no more floor space is then occupied than with 
hand-firing; but it is often advantageous to use an extension furnace 
or Dutch oven. The Dutch oven is generally the best arrangement 
for burning sawdust, shavings, tan bark, bagasse and similar fuels, 
owing to the large furnace chamber desirable and the convenience 
of the top-feed. Methods of applying stokers and furnaces are 
shown in Chapters 4 and 5. 



34 




X \."^-"\-'S'T'X 



Heine Standard Superheater. 



HEINE PRACTICE 35 

Operation of Heine Boilers 

THE water circulation and steam separation in the Heine Boiler 
are absolutely definite. The capacious headers and large throat 
openings allow a freedom of flow unattainable with sectional 
headers. The throat openings are from two to four times the area 
of the tubes which connect sectional headers to their drums. The 
resistance at the entrance of these tubes and of the zig-zag path 
along sectional headers is a further obstruction to circulation. Heine 
box-headers are common to all the tubes, and water enters the tubes 
round their whole circumference, whereas side-entry is cut off in 
sectional headers. The slope of the Heine drum provides deep water 
at the rear for the effective supply of the back header. 

The water rises through the large throat into the Heine drum at 
a suft'iciently low velocity to allow of efficient separation of the 
steam by the deflector plate ; while the steam and water is shot 
with considerable violence from the single tubes of sectional headers, 
making the drying of steam uncertain. 

The water surface in the drum is more than ample, for steam 
is not disengaged from it as in tank and fire-tube boilers. What 
little circulation there is in fire-tube boilers, is entirely haphazard, 
and the water surface must be large because the steam is disengaged 
at any point. In the Heine Boiler the circulation is vigorous and 
orderly, and the steam is separated from the water by a properly 
arranged deflector at a definitely established point over the front 
throat passages, page 46. The deflector plate throws down the water 
and allows the steam to pass quietly into the steam space above ; it 
then enters the dry pipe connected to the steam outlet. 

A salient feature of the Heine Boiler is the internal mud drum, 
in which the feed-water is partly purified and heated to the boiling 
point before it enters the water in circulation. The feed-water 
pipe enters through the top of the drum and passes down to the 
front end of the mud drum. The mud drum is entirely submerged ; 
and as the entering water is colder and therefore heavier than 
the water already inside, it travels along the bottom and becomes 
heated gradually. The mud drum is large enough to permit of such 
slow motion of the water that the dissolved impurities thrown down 
at steam temperatures have time to be deposited, together with mat- 
ter carried in suspension. As the water becomes heated, it rises and 
finally flows in a thin sheet, through the opening in the top of the 
front end of the drum, into the circulation system. It is therefore 
possible to drive the Heine Boiler at heavy loads with very cold feed- 
water. As the matter deposited is not subjected to fire tempera- 
tures, it does not tend to become baked and hard, but remains as a 
sludge easily blown out through the pipe at the rear of the drum. 




Q 



c 
o 

o 

(U 
u 

w 

o 

(4-1 

CO 
0) 



o 
PQ 

G 



o 
J3 



HEINE PRACTICE 37 

Because of the internal mud drum, the Heine Boiler works much 
more satisfactorily than any other boiler when only cold and dirty 
water are available. But it is always more economical to treat 
impure water before feeding it into the boiler, and to pre-heat it 
with waste steam or waste hot gases. 

The boiler is drained through a valve at the bottom of the rear 
waterleg. The steam connection of the water column is made at 
the top of the front head, and the water connection at the top of the 
waterleg. The pressure gage is attached to the middle of the orna- 
mental front and piped from the water column connection. 

The gases of combustion — whatever type of furnace or stoker 
is used — pass over the bridge wall into a large combustion chamber. 
The bridge wall is low enough to provide ample area between its 
top and the tubes. The large combined capacity of the furnace 
and combustion chambers is one of the outstanding merits of the 
Heine Boiler. Plenty of time and space is provided for the thorough 
mixture and complete combustion of the gases before they come 
in contact with the comparatively cool heating surfaces. This pro- 
vision for complete combustion, and the consequently improved 
efficiency and reduction of smoke has been proved so valuable that 
the Heine method has replaced the vertical baffling of many hori- 
zontal water-tube boilers and has even replaced the method of 
baffling of some types of vertical water-tube boilers. 

In Heine Boilers, the gases travel parallel to the tubes, except 
when entering and leaving the tube bank. This parallel flow is used 
whether the gases make one or more passes. With parallel flow, the 
gases completely encircle the tubes. When the gases flow across the 
tubes, as in cross- or vertically-baffled boilers, a dead pocket occurs 
on the ''down-stream" side of each tube. This effect can be seen 
by watching the almost stagnant water at the down-stream side of 
the piers of any bridge crossing a swiftly flowing river. Owing 
to the close tube spacing possible by the rational design of Heine 
header, the gases are broken up into smaller streams than is usual, 
so that the whole volume of gas is brought into intimate contact 
with the tube surface. That more efficient heat transmission is 
attained with parallel flow than with cross flow, has been frequently 
demonstrated in tests of cross-flow boilers that have been changed 
to parallel-flow. 

It is important that the gases should be kept in contact with the 
heating surface until all the available heat is absorbed. In all cross- 
or vertically-baffled boilers, however, the gases are twice taken 
entirely away from the tubes, where they waste heat by radiation. In 
addition to the evident waste of heat, the hot gases from the first 
pass flow along the bottom of the drum causing ebullition in the 
wrong place, the avoidance of which should be one of the main 
advantages of the water-tube boiler. Another advantage of the 




Q 



Xi 
(L> 
4J 
O 
V 
U 

W 

c 

(U 

3 
6 

D 
CO 






C 

o 
Q 

ID 
U 

o 

c 



o 
pq 

(U 
CO 

•-) 

a 

"a 
a 

CO 

(*-■ 

o 
o 

J3 



HEINE PRACTICE 



39 



water tube boiler— that of keeping hot gases away from the drum 
and from riveted joints — is absent in cross baffled boilers. In the 
Heine Boiler, the gases are confined to the tube bank until they 
have parted with nearly all of their available heat. Not until then 
do they come in contact with the drum; consequently the last of their 
useful heat is given up without disturbing the quiet flow of solid 
water to the rear. 

The construction of the Heine Boiler combines sturdiness and 
resiliency. Water is boiled and steam generated in the bank of tubes 
and not in the drum or shell The gases are kept where they belong 
—among the tubes — until discarded to the uptake. The circulation 
path is farge and unrestricted, making the flow of water and steam 
slow enough for efficient separation— or for dry steam and a solid 
water stream. 



^ 




Soot Blowing System, Side Elevation. 



HEINE PRACTI CE 



41 



Cleaning of Heine Boilers 

ALL cleaning — both inside and out — is performed from the front 
and rear. There are no openings in the sidewalls, or aisles 
between boilers. 

Soot and dust are blown from the tubes by a soot blower, 
which is provided with every Heine Boiler. It consists of a 
series of small nozzles which pass through the hollow stay-bolts, and 
which are supplied from permanent headers, so that the only manual 
labor required is to open and close the valves. The jets of steam 
issuing from the main nozzles create an intense momentary draft 




Rear 

View 



o O'-o^a'O'O'O'O'O o' 
I di'o°o«q£p<'0<>c>o°o»a- ' 



0°OaO°0°OiP'0°OaO»Q-'^ 



imifMloP 



.o9^# ig9fg#oj'S ?J 




Soot Blowing System. 




Standard Fire Front of Heine Cross Drum Boiler. 



HEINEPRACTICE 43 

which effectively dislodges the soot and dust and carries it to the 
uptake. The auxiliary jets are so located as to stir up accumula- 
tions on the baffling and in all corners. This work is done in a few 
minutes, generally during the noon rest, or just before or after 
closing down at night. It is so easy as to be entirely out of com- 
parison with the old-fashioned *'steam-lance," whose use is naturally 
neglected whenever possible. Thorough cleaning is immediately 
profitable as may be seen by the quick drop in temperature of the 
exit gases. 

Cleaning doors are provided on each side of the drum so that 
accumulations of dust and soot can be easily and quickly removed 
from the space over the upper baffle beneath the drum. The com- 
bustion chamber is cleaned through a door in the wall under the 
rear waterleg. 

The interior of the drum is thoroughly inspected through the 
manhole in the rear head, which also permits of attention to the 
mud-drum, deflection plate^ etc. 

The inside of the tubes is washed by a stream of water directed 
through some of the handholes. Only a few of the handholes need 
be opened for this purpose, since each gives sufficient access 
to four or five of the surrounding tubes. In scraping the tubes, 
however, each handhole must be opened to admit the scraper, 
although in both this and the washing process the handholes at one 
end only are opened. 

As only straight tubes are used, every part of the boiler can be 
reached, properly and quickly cleaned, and visually inspected, so 
that there is absolutely no uncertainty as to its condition. 

Renewing tubes is done from the outside as in cleaning tubes, 
the men standing erect and working comfortably and quickly. The 
inside of the box-waterleg is easily cleaned and inspected, because 
all the hand holes give light and access to one space. 

Heine Cross Drum Boiler— Land Service 

THE Heine Cross Drum Boiler for land service, page AA, consists 
of two box headers carrying a nest of inclined tubes and of a 
drum placed above and across, slightly to the rear of the front or 
lower header. The drum is connected to the top of each header by a 
row of tubes — short, nearly vertical, to the front header — and long, 
nearly horizontal, to the rear header. 

The main nest of tubes, with the headers, form a virtually 
closed or complete circulation system of remarkably low resistance 
owing to the capacious headers. The steam rises in the rear header, 
where its primary separation from the water is promoted by a 
device at the upper part. It then flows along the almost horizontal 
tubes, parting with most of the entrained water by gravity, to 
the final separator in the steam drum, where it is dried by centri- 
fugal action set up by a deflector. The water carried into the drum 



44 




Longitudinal Section of Heine Cross Drum Boiler with 
Chain Grate Stoker. 



HEINE PRACTICE 45 

is returned, together with the new feed water, to the circulation 
system through the short tubes leading into the top of the front 
header. Steam is drawn from the ample storage space through a 
dry pipe extending nearly the whole length of the drum and pro- 
vided with small holes on the upper side. 

This closed circulating system and the means used in collecting 
and drying the steam while maintaining quiet water in the drum, is 
the outcome of exhaustive and prolonged research into the direction 
and velocity of flow in the different rows of tubes. As a result the 
tubes and baffling have been so proportioned and arranged that the 
overload performance of Heine Boilers of this type is acknowledged 
by users as a notable achievement. 

The mud-drum is constructed and operated on the same prin- 
ciple as that employed in the longitudinal drum boiler, described on 
pages 19 and 35. The movement of the feed-water therein is very 
slow, so that dissolved impurities which are thrown down at steam 
temperatures are deposited, as is matter carried in suspension. As 
the deposit is not hardened by exposure to fire temperatures, it 
remains as an easily blown-off sludge. Owing, also, to the slow 
movement of the feed water in the mud drum, it is heated to the 
boiling point before passing into the circulation system, so that 
Heine Boilers can be heavily driven with cold feed water. As the 
water issues from below the surface in the mud-druVn, any oil accu- 
mulated does not enter the boiler proper, but is discharged through 
the blow-off. 

Except in large boilers, the drum is made of a single sheet, with 
longitudinal double-strapped butt-joints. The heads are dished to a 
radius equal to their diameter, so that internal staying is not re- 
Cjuired. One head is generally provided with a flanged manhole 
with pressed steel cover and yoke ; but when more than two boilers 
are set in battery, the manholes of all but the end boilers are placed 
in the drum proper instead of in the head. 

A reinforcing plate is riveted to the drum, where each row of 
tubes enters. Forged steel pads are provided for the feed, blow-off, 
and water column connections, and pressed steel saddles, page 44, 
for safety valve and main steam outlet — all shaped to a snug fit on 
the drum, and either threaded or with stud-bolts to fasten the 
connections. 

The box headers consist of two heavy steel plates with long 
radius flanging at top and bottom and with flat parts formed at the 
proper angle to allow the drum tubes to enter squarely ; these plates 
are fully annealed before assembling. They are connected by a 
single-riveted lap joint, no butt straps being required. The resulting 
boxes are closecl by trough-shaped end-plates, flanged by hydraulic 
machinery at a single heat to a close fit, and riveted to the side 
plates. The holes in the tube and handhole sheets are accurately 
located and bored to exact diameters to secure proper angular 
relation between the drum tubes and those of the main bank. 



46 







o 



•a 

c 

C3 

-4-1 

w 

.s 



c 
o 

o 



CO 

.s 

•5 

•4-> 

c 
o 



HEINE PRACTICE 47 

These headers are stayed by hollow staybolts, page 25, of tested 
seamless tubing, which are screwed into tapped holes in both plates 
and the projecting ends neatly upset. 

The handholes are opposite the tube ends and are closed by one 
of several methods — cast iron or drop forged steel plates and gaskets 
making joints on the inside, or the Key handhole caps which are 
expanded in and require no gaskets, page 27. 

The tubes are the best quality lap-welded mild steel, made espe- 
cially to Heine specifications. They are 35^-in. diameter, secured 
by roller expanders and the ends flared for additional strength. 

The steam drum and the lower header are usually at the front end 
of the boiler, but to save head room this arrangement can be reversed. 

The front of the boiler is carried by columns which are secured 
to heavy lugs riveted to the header end plates. These columns are 
made of any length to give the desired height of furnace. Similar 
heavy lugs are riveted to the rear header, and these are connected 
to the rear columns by massive suspender bars. This provides a 
flexible support which allows for expansion and contraction due to 
temperature changes. 

The whole boiler is enclosed by brick side-walls, the rear wall 
being underneath the rear header. The top is closed by fire-brick 
and insulating covering, carried by T-bars resting on the side-walls. 

Casing doors at front and back give access to the headers for 
cleaning and inspection. 

Safety valves of proper size, a large high and low w^ater alarm 
column with quick acting shut-ofif device operated from the floor by 
chains, and three try cocks, are provided. A steam gage is attached 
to the boiler front, and feed, check and blow-of? valves are supplied 
and located so as to be easily accessible and conveniently manipu- 
lated. The required buck-stays, cleaning doors and anchor rods are 
supplied. 

The soot blower system applied to the cross-drum boiler consists 
of the nozzles inserted through the hollow staybolts of the rear 
header. The main jets create an intense momentary draft, which 
dislodges the accumulations from the tube surfaces and carries them 
to the uptake. Auxiliary nozzles are so located as to stir up and 
dispose of any accumulations on the baffle tiling. 

Heine Marine Boilers 

THE Heine Cross Drum Marine Boiler, page 50, is similar to the 
cross drum boiler for land service, the main difference being that 
it is shorter due to the lack of space. The standard marine boiler 
has 3^-in. tubes throughout ; but for oil-fuel, space is saved and sat- 
isfactory results obtained by the use of 2-in. tubes in the main bank. 




o 

a 



73 



u 



o 

m 

X 
'a 

C/2 



o 

J! 



HEINEPRACTICE 49 

For low or medium superheat temperatures, superheaters of the 
type used for land installations are fitted. They are of the "waste- 
heat" kind, placed in the base of the uptake, as close as possible to 
the exit of the gases from the boiler. For higher superheat, the 
elements are passed through the middle of the main tube bank, where 
they are in contact with gases of high temperature. 

In ocean service the feed water cannot be kept entirely free from 
sea water, which sets up electrolytic action. Zinc plates are there- 
fore placed in the drum to act as the electro-negative agent and 
prevent corrosion. In the Heine Marine Boiler the United States 
Navy standard is used — ^ sq. ft. of exposed zinc for each 100 sq. ft. 
of heating surface — and the zinc plates are so secured as to ensure 
perfect electrical contact with the metal of the boiler. At the same 
time they are easily removable. A pressed steel basket is provided 
to catch the disintegrated zinc. 

The setting consists of a framework of rolled steel shapes so 
constructed that the four main columns — one on each side of each 
box header — are tied and securely braced against any motion. This 
framework carries a steel plate casing lined with firebrick, non- 
conducting material, or a combination of the two. 

The construction and operation of Heine Marine Boilers is 
explained more completely in another Heine publication — Marine 
Boiler Logic — which is sent upon request to those interested. 



Standard Boiler Specifications 

A NATIONAL and even an international standard of steam- 
boiler design is represented by the Boiler Code formulated in 
1914 by the American Society of Mechanical Engineers, and since 
that time kept up to date by frequent revisions. The value of the 
Code is indicated by the fact that it has been adopted by more 
than tw'elve states in this country, by foreign countries, and by 
branches of the U^nited States Government. 

For many years the necessity of uniform boiler specifications 
has been recognized both by makers and users of boilers. In 1889, 
the American Boiler Manufacturers' Association adopted what were 
known as the Uniform American Boiler Specifications. These speci- 
fications, which were revised in later years, gave information 
relating to material, construction and calculation for all kinds of 
boilers. In this fundamental work Col. E. D. IMeier, founder and 
president of tlie Heine Safety Boiler Co., until his death in Decem- 
ber, 1914, took an important part. Colonel Meier was chairman of the 
committee which prepared the first specifications in 1898, was presi- 
dent of the American Boiler Manufacturers' Association from 1908 
to 1914, and was its secretary for several years previous to 1908. 



50 



WATCRUINE 
GAUGE 6LAS 
CHECK 
VALVE 




DRAIN PAN 
COUNTERWEIGHT 



FIRE 



ASK DOOR 
FRONT COLUMN 



Longitudinal Section of Heine Cross Drum Marine Boiler. 



HEINE PRACTICE 51 

In 1907 a board was appointed by the state of Massachusetts to 
prepare a set of boiler rules. The members of this board repre- 
sented different boiler interests, such as the users, makers, insur- 
ance companies, and operating engineers. The chairman of the 
board was the chief inspector of the Massachusetts Boiler Inspec- 
tion Department. The Massachusetts boiler rules were issued in 
1909 and engineers considered that they represented a real advance 
in the art. From a national standpoint, however, the Massachusetts 
rules simply made one more set of conditions with which the boiler 
manufacturers and users had to comply. A boiler that is safe in 
Massachusetts certainly should be safe in any other state of the 
Union, but practically every state (at least in 1911) had special re- 
quirements for boiler construction, and these were rigidly enforced. 

The remedy for this condition was found by Colonel Meier; he 
had already noticed the beneficial working of the Steamboat and 
Locomotive Inspection Laws under Federal control. The best an- 
swer to the problem was to have the different states adopt uniform 
specifications for boilers, since a constitutional amendment would 
be required to put stationary boilers under Federal supervision. The 
different state legislatures and other authorities were willing to 
use such specifications, provided they could be assured of their value. 

In 1911 Colonel Meier, then president of the American Society 
of Mechanical Engineers, suggested that a committee of the Society 
"formulate standard specifications for the construction of steam 
boilers and other pressure vessels and for the care of same in 
service." This committee came into existence on Sept. 15, 1911, and 
was instructed to formulate a model engineers' and firemen's license 
law, a model boiler inspection law, and a standard code of boiler 
rules. Its first chairman was John A. Stevens, who had been a 
member of the Massachusetts Board of Boiler Rules. The boiler 
makers were represented by H. C. Meinholdt, vice-president of the 
Heine Safety Boiler Co. Upon Mr. Meinholdt's death in 1913, 
Colonel Meier was appointed a member of the committee. The 
other members represented different interests connected with boiler 
operation and construction. 

Three years were devoted to hearings and consultations. The 
Code was finally presented at the Annual Meeting of the American 
Society of Mechanical Engineers, in December, 1914, and on Febru- 
ary 13, 1915, it was approved by the Council of the Society. In 
preparing the Code every source of information was utilized, in 
order that the boiler situation should be thoroughly covered. Colonel 
Meier's original committee of seven members was assisted in the 
final preparation of the Code by eighteen notable boiler specialists in 
the design, installation and operation of boilers. 




The First Heine Boiler, Built in 1882. Still Good for High Pressure 
after Thirty-five Years of Continuous Service. 




Comparative Sizes of the First Heine Boiler and a Standard 

500 H. P. Boiler. 



HETNE PRACTICE 53 

Although in ill health, Colonel Meier was interested in the Code 
until his death. According to John A. Stevens, Chairman of the 
Code Committee : 

"Colonel Meier took a most active part in the formation of 
the A. S. M. E. Boiler Code, and up to within a few days of 
his death, had it constantly before him. It is one of the 
regrets of the Committee that he could not have lived to see 
the fruition of the work he so w^isely started." 

The Boiler Code is too long to give in full here, but can be 
obtained from the American Society of Alechanical Engineers, 
29 West 39th Street, New York, by the payment of fifty cents. The 
Code is divided into two parts, the first applying to new installa- 
tions, and the second to existing installations. 

The Code as completed is much more far-reaching than the 
Massachusetts Rules. Quoting Mr. Stevens again, 'Tt specifies in 
detail the chemical and physical properties of all materials entering 
into the construction of boilers, and gives rules, formulas and tables 
that have been checked and rechecked by men of national reputa- 
tion, and in many cases verified by testing laboratories ; that is to 
say, in many cases, rules or formulas were withheld until actual 
tests in laboratories were made in order to prove the mathematics." 
The Committee formulating the Code has been made permanent, 
and holds regular meetings for the purpose of interpreting any 
points on which questions are raised. From time to time the Code 
is revised to include the latest knowledge of steam-boiler con- 
struction. 

The work of bringing the A. S. M. E. Boiler Code into use is 
being done by the American Uniform Boiler Law Society, which is 
carrying on an educational campaign in the states that have not yet 
adopted the Code. The Society is made up of representatives of 
the organizations interested in the construction or operation of steam 
boilers. In many states laws have been passed creating a board of 
boiler rules. Such boards are authorized to adopt the standard 
A. S. M. E. Code, and to amend it in accordance with the amend- 
ments made by the Society. 

State legislatures and authorities move slowly along engineering 
lines, but the use of the Code is increasing, and in time it undoubt- 
edly will be adopted in every state of the Union. At present "Code" 
boilers are required in certain states, but in others boilers built to 
less rigid rules can be installed. 

All Heine Boilers, no matter in what state they are used, comply 
with the requirements of the Code. The Heine Company is also 
assisting in its adoption through the work of its executives on 
the Code Committees of the American Society of Mechanical Engi- 
neers, the American Boiler Alanufacturers Association and the 
American Uniform Boiler Law Society. The Company believes 
that the Code should be adopted not only in every state in this 
country, but should also be made international in scope. 



54 




a 

OS 

U 



o 

c 

CO 

X 
>> 

V 



u 
V 

'o 
•PQ 



J3 

3 
O 

Q 



CO 
CO 

w 
.5 



55 



CHAPTER 2 



BOILER RATING AND DESIGN 

THE rating of a machine should naturally be expressed in terms of the 
useful work done by the machine. The useful work done by a boiler is 
represented by the heat transferred to the water in the boiler ; thereby 
causing evaporation, > 

In actual practice boiler pressures, initial steam conditions and feed 
water temperatures vary widely. If performances are to be compared, 
they must be reduced to an equal basis. The actual evaporation is therefore 
referred to an equivalent evaporation from a feed water temperature of 
212 deg. into dry-saturated steam at the same temperature, or as it is com- 
monly expressed, "from and at 212 deg. Fahr." 

The heat added to each pound of water under these conditions will then 
be L at 212 deg. The 1915 A. S. M. E. Boiler Code stipulates that this 
quantity is 970.4 B. t. u. per pound. Goodenough gives a slightly higher value 
(971.7) which is probably more accurate. 

The heat actually absorbed by one pound of water while in the boiler will 
be H — q, where H is the heat content of the steam as it leaves the boiler 
— it may be wet-saturated, dry-saturated or superheated — and q is the heat 
of the liquid at the temperature of the feed water entering the boiler. 

gives, therefore, the pounds of water evaporated from and at 212 deg. and 
equivalent to the actual evaporation of one pound. 

This quantity F is called the "factor of evaporation." When multiplied 
by the pounds of water fed to the boiler for any given time, the product is 
the equivalent evaporation from and at 212 deg., expressed in pounds for 
thnt time. This equivalent evaporation is usually expressed, however, in 
pounds per pound of coal. 

Boiler Horse Power 

A boiler horsepower was originally defined as the actual evaporation 
of 30 lb. of water per hour from feed water at 100 deg. into dry-saturated 
steam at 70 lb. gage pressure. When the term "equivalent evaporation" 
came into use, however, it was applied to the boiler horsepower, which is 
now defined as the equivalent evaporation of 34.5 lb. per hour from and at 
212 deg. 

A formula for finding this term would be expressed thus : 
, , p __ (H — q) (lb. H,0 fed per hr.) ^ F X lb. H.O fed per hr. (2) 
971.7X34.5 ~ 34.5 

The boiler horsepower and the engine horsepower are in no way related. 
When the original boiler horsepower unit was selected a one horsepower 
boiler would supply a one horsepower engine. Increase in the economy of 
engines, however, has changed that ratio until now a 100 horsepower boiler 
will supply 250 engine horsepower, at least. 

The term boiler horsepower has thus lost much of its significance. 
Almost any modern boiler will run continuously at from 150 to 200 per 
cent over its rating and for short periods 400 and even 500 per cent have 
been reached. 




Lowering Heine Standard Boiler into Hull of Dredge Boat "Texas" 
The Atlantic, Gulf & Pacific Company. 



of 



BOILERS 57 

Heating Surface 

The better measure of boiler capacity is the heating surface. Heating 
surface is that surface which has hot gases on one side of it and water or 
steam on the other side. By the A. S. M. E. code, it is the surface "in con- 
tact with fire or hot gases." In all water-tube boilers and in most fire-tube 
boilers (the common vertical and Manning types are exceptions) the whole 
surface of the tubes is heating surface. Tube heating surface constitutes by 
far the greater part of the total, in any type of boiler. As boilers are built, it 
is usually the most effective part, except in internally-fired boilers. Additional 
heating surface is provided in horizontal tubular boilers, by the shell up to 
the line where the setting racks in, and by the heads up to the same level. 
The inner faces of the waterlegs, and part of the drum shell, in a Heine 
boiler are heating surface. 

Formerly 10 or 12 sq. ft. of heating surface was allowed per boiler 
horsepower. The corresponding rate of evaporation was usually around 3 lbs. 
of water per sq. ft. of heating surface per hour, for it was observed 
that if the rate of evaporation greatly exceeded 3 lbs. per sq. ft., the 
increase of coal consumption outran the gain in water evaporation, and the 
flue gas temperature became high. In good modern design, rates of evapora- 
tion much higher can be secured without serious sacrifice of efficiency. 
As high as 10 lb. is frequent in marine practice. From 4^ to 6 lb. is 
justified in power stations carrying highly variable loads, the slight loss in 
economy being more than offset by the reduced investment for boilers and 
power house space. The obtaining of these higher rates of evaporation 
is chiefly a matter of draft. Their attainment without a serious sacrifice of 
efficiency is a matter of boiler design. The proportions, tube sizes and 
spacing, baffling and general arrangement must all be properly worked out. 
The higher rates cannot be obtained at all with certain types, the common 
vertical boiler being an example. 

The cost of a given boiler, and also its size, varies almost directly with 
the amount of heatmg surface. Hence the desirability of high rates from 
an investment standpoint. 

Grate Surface 

The grate surface is important in determining the capacity of a boiler, 
although related only indirectly to its efficiency. The rate of combustion 
depends upon the kind of fuel and the draft. The latter may be determined 
by reference to the chart given in Chapter 5 on CHIMNEYS. 

For oil, there Is no grate, and capacity Is based upon furnace volume. 
In marine work a maximum oil consumption of 10 lb. per cu. ft. of furnace 
volume per hour Is permissible, but In land practice much less than this is 
allowed. 

The grate surface required for hand-fired boilers under normal opera- 
tion can be found bv : 

^_ 33,480 H. P. (3) 

B K E 

G == Total grate surface, sq. ft. 
H.P.=^ Horsepower rating of boiler. 

B = Heat value of coal, B. t. u. per lb. 

K = Rate of combustion per sq. ft. of grate per hr., lb. 

E ^=: Combined efficiency of boiler and furnace, per cent. 



58 



BOILERS 



Heating Surface Ratios 

A ratio of 1 sq. ft. of grate area to 35 or 40 sq. ft. of heating surface is 
■common for boilers that operate at rated capacity, when burning commercial 
sizes of anthracite. For overload capacity the ratio is taken at about 1 to 25, 
and for burning low grade coals a forced draft system is necessary. For 
bituminous coals, the ratio of grate area to the boiler heating surface runs 
as low as 1 to 30, and as high as 1 to 70 in different instances. L. S. Marks 
recommends the ratios, of grate proportions to operating economy and boiler 
capacity, given in Table 1. 

Table 1. Heating Surface Ratios — Bituminous Coals. 



Name of Coal 



Ratios of Grate Surface to Heating Surface 



For Economy 



For Capacity 



i Run of 
I Mine 



Slack 



Run of 
Mine 



Slack 



Grate Bar Openings, 
Inches 



Run of 
Mine 



Slack 



Va., W. Va., Neb., Pa. 
Ohio, Ky., Tenn., Ala. 
111., Ind., Kan., Okla.. 
Colo., Wyoming 



1 to 60 
1 to 55 
1 to 50 
1 to 50 



1 to 55 
1 to 50 
1 to 45 
1 to 45 



1 to 55 
1 to 50 
1 to 45 
1 to 45 



1 to 50 
1 to 45 
1 to 40 
1 to 40 



% 



Va 



Heat Transfer 

The rate of transmission of heat through the boiler surface depends 
chiefly upon the difference in temperature between the hot gases and water 
on the two sides of the heating surface, and upon the rate of movement of 
the two fluids across the surface. For those surfaces directly exposed to the 
fire, the transmission is due chiefly to radiation, which varies as some power 
of the temperature difference. A sustained high temperature in this region is 
therefore important. Other surfaces act more by convective transmission. 
The fluid flow then is of chief importance, the transmission varying about 
as the first power only of the temperature differences. As forced water 
circulation is not employed in large boilers, the water flow cannot be con- 
trolled at will. In general, the harder the boiler is driven, the better will 
be the water circulation, which is the condition desired. 

The heating surface directly exposed to the fire does most of the work. 
Gehhardt states that this would be true even if the furnace transmission 
varied as the first power only of the temperature. Here the last 20 per 
cent of the surface reduces the flue gas temperatures only 65 deg. This 
is of course an understatement. Allowing for the much greater effective- 
ness of that portion of the surface immediately adjacent to ths furnace, the 
last 20 per cent must necessarily reduce the flue temperature considerably less 
than 65 deg. Even at 65 deg., however, with ordinary operation, the omission 
of the last 20 per cent of the surface would cause a loss of only about 300 
B. t. u. per pound of coal, or about 2 per cent. Hence where first costs are 
high or loads variable the ratio of heating surface to grate surface should 
be low. Hence also the slight loss of efficiency due to increasing rates of 
evaporation. In European practice, the heating surf&ce has been strictly 
limited and economizer surface employed to obtain low final stack tempera- 
tures. The fluid temperature difference is greater at the economizer, so 
that one square foot of economizer surface more than replaces a square foot 
of boiler surface. 

See Chapter 11 on HEAT. 



BOILERS 59 

Gas Passages 

Gas circulation is subject to control both in design and operation. Since 
the effort is made to have all of the gas strike all of the heating surface 
(thus keeping down the flue temperature and stack loss), the gas velocity 
at a given rate of driving is determined solely by the nature and dimensions 
of the gas passages. Formerly certain proportions of the grate surface were 
allowed for the cross-sectional area through or around tubes, but the results 
were only accidentally correct. With proper operation, the kind and weight 
of coal to be burned per hour determines within reasonable limits the weight 
of gas produced per hour. The volume of this gas depends upon its tempera- 
ture, and the rate of decrease of temperature from furnace to stack has 
been determined by experiments for certain boilers. The velocity of this 
gas depends upon the draft (which is related to the rate of combustion) and 
upon frictional resistance, all of which can be valuated with fair accuracy. 
The volum.e and the velocity being known, the cross-sectional area necessary 
for gas passage can be calculated. With high draft, small area and high 
velocity, gases yield their heat at a rapid rate, but they are also moving to 
the stack at a rapid rate. The best rate of yield as compared with 
rate of movement determines the cross-sectional areas. For anthracite coal 
at low rates of combustion, the old rule was to use 1/7 of the grate surface 
for the area over the bridge wall, 1/8 for the flue area and 1/9 for the 
chimney area. Areas naturally decrease from passages near the furnace 
to those near the stack. 

Areas for gas passage can be correct, and operation nevertheless unsatis- 
factory, if the details of the baffling are wrong. The gas should as far as 
possible be compelled to strike the surfaces without indulging in short cuts or 
leaving dead spaces where the circulation is sluggish. A boiler is a machine, 
the moving parts being gas and water, and these motions must be correct 
if efficiency is to be good. 

Baffling 

PARTITIONS are placed among the tubes to direct the flow of the hot 
gases. These baffles can be vertical, causing the gases to flow across 
the tubes ; or horizontal, so that the gases travel the length of the tubes. In 
selecting the design of baffling for a given installation, its flexibility, ease and 
cost of upkeep, and influence on heating surface must all be considered. In- 
vestigations by the Bureau of Mines show : 

(1) A boiler whose heating surface is arranged to give long gas passages 
of small cross-section will be more efficient than a boiler in which the gas 
passages are short and of larger cross-section. 

(2) The efficiency of a water-tube boiler increases as the free area 
between individual tubes decreases and as the length of the gas pass 
increases. 

(3) By inserting baffles so that the heating surface is arranged in 
series with respect to the gas flow, the boiler efficiency will be increased. 

These results point to the desirability of horizontal baffles and the 
importance of the long, unchilled flame and the large furnace volume ob- 
tained by their use. 

The entire heating surface in a boiler is not active, because of the 
eddies peculiar to gas flow. With practical baffling, the inactive surface 
caused by dead gas pockets can be minimized. 

During tests by W. N. Polakov on the vertically baffled boiler, shown 
in Fig. 1, pyrometer measurements showed that only about 60 per cent 
of the surface was an active heat absorber, the remaining 40 per cent repre- 
senting the dead pockets. Horizontal baffles may not eliminate the dead 
regions, but they can reduce the inactive surface considerably by decreasing 




u 

a 

CO 

d 

C 



5 -^ 

C <U 

cs a 

CO t? 



(U .J-. 

o 
c o 

CO u 



CO 



PQ J« 

o nn 
u ^ 

. c 



a 
a 
u 

Oh 
1) 



e 

o 
o 



o 



61 



Feed Wafer 
Thermomeier 



Thermomeier for 
Superheated 
Sfeam--->^ 



Q^ ^5 b5 



Draff 
Gage to 
Draftin 
Furnace 



Draff 
Gage in 
Ashpit • 




.l<$^l\\V^s\\:^;^^^^x-^s^^^\^x^^ 



\r 



Fig. 1. Dead Regions in a Vertically Baffled Boiler. Shaded Parts show 

Inactive Surface. 



c 

lE 

(^ 
o 

c 

u 

E 

o 
o 

-f- 



700 



600 



500 



400 



300 



200 































^ 






1 1 1 
X PocahonfofS 
f^Clinchfield 

I 1 1 












S 


^ 


X 


^- 














,^-^ 


.^< 


> "^ 


O 


> 

u.--' 














r 


,5 ^ 


^* 


^ 


^ 


"o. 


.>^^ 




b ^ 










■w^' 


t^- 




J.f< 


s^. 


^H 


X " 










..^ 


^ 


\iorpP^ 


n^ji. 














1 


J 


«*" ^^ 




^' 






vH 


"Steam 


Tzmperafure 363° F. \ 






























1 

1 































































o 
«-o 



o 
o 



o 



Fig. 2. 



Boiler Capacity, Pcrcen+ 

Comparison of Stack Temperatures in Test Boiler when Baffled 
Vertically and Horizontally. 



62 



BOILERS 



the size of the dead comers. In Heine boilers, Fig. 5. a large percentage 
of the tube surface absorbs heat because of the battle construction. 

Horizontal baffles are recognized as standard for smokeless settings. 
Smokeless combustion usually cannot be obtained with verticalh^ baffled 
boilers unless the setting is ven,* high. With hand-firing and bituminous 
coal, vertically baffled boilers are not allowed where smoke ordinances are 
stringent. For this reason horizontal baffling has been applied to many 
boilers designed originally with vertical baffling. By substituting the hori- 
zontal for the vertical pass, a longer flame travel between the furnace and 
the tube region is obtained, without increasing the floor space. 

In tests by Henry Kreisinger and M. T. Ray, the draft through the 
verticalh' baffled boiler was 0.5 in. for an average load of 128 per cent. 
When the same boiler was baffled horizontally, the draft was only 0.375 in. 




K^t^TT, 



i^^^^^^^^^^^^p' 



Fig. 3. Original Vertical Baffling of Test Boiler. 




Fig. 4. Two-Pass Horizontal Baffling of Test Boiler. 



BOILERS 



63 



at 127 per cent load, with the same CO. percentage. These tests were con- 
ducted to determine whether horizontal passes gave good results when 
burning Pocahontas and CHnchfield (high-volatile) coals. 

Nineteen tests were run under actual plant operating conditions with the 
same boiler, baffled as shown in Figs. 3, 4, and 5- Table 2 summarizes these 
tests. The flue-gas temperatures at the different boiler loads are shown in 
Fig. 2. At 120 per cent capacity, the average temperature with the vertical 
baffles was 590 deg., and with the horizontal baffling only 500 deg. 



V///y,v.../.y//WMMW.v.'/ >^^^jyy/,>,y^//^^ ^^ ^ .v.yy/^v^w v. ^ ■>. 




'/ABsr/Ac///*^--.' - ■^-■- ---T^J^al|^>^ g'K^'-v^^^^^ 



Fig. 5. Three-Pass Horizontal Baffling of Test Boiler. 



Table 2. Results of Boiler Tests with Different Baffling. 





Original (Vertical) 


Two Horizontal 


Three Horizontal 




Baffling 


Passes 


Passes ''■ 


Name of Coal 


Poca- 
hontas 


Clinch- 
field 


Poca- 
hontas 


Clinch- 
field 


Poca- 
hontas 


CHnch- 




field 


Number of tests averaged. . . . 


4 


3 


4 


3 


4 


3 


Water evaporated under 














actual conditions per lb. 














of coal as fired, lb 


7.95 


7.49 


8.54 


8.18 


8.8:3 


8.52 


Equivalent evaporation 














per lb. of coal as fired, 












■ 


b 


9.42 


8.90 


9.92 


9.61 


10.33 


9.97 


Average hp. developed 


320 


285 


335 


357 


303* 


298* 


Maximum hp. developed. 


341 


297 


355 


365 


317 


311 


B. t. u. per lb of dry coal 


14,828 


14,122 


15,050 


13,801 


14,731 


13,750 


Ash, per cent 


4.9 


7.9 


4.72 


10.26 


5.5 


9.85 


Approximate efficiency of 














boiler and furnace, per 














cent 


61.3 


60.9 


63.6 


67.2 


67.7 


69.9 



*0n the test with three horizontal passes, higher capacity could have been developed, but the 
feed water was too hot and the injector would not feed it fast enough into the boiler 



BOILERS 



65 



When the boiler is baffled horizontally much better results can be 
obtained with high-volatile coal. There is also a marked improvement, when 
the horizontal baffling" is used, for Pocahontas coal. The horizontal three- 
pass baffling gave the highest evaporation and the horizontal two-pass 
developed the highest horsepower. With the two-pass horizontal baffling 
higher evaporation and horsepower can be obtained with Clinchfield coal, 
than with vertical baffling and the higher grade Pocahontas. The draft 
loss through the boiler is less for the horizontal two-pass than for the 
original vertical baffling. The number of turns taken by the gases is the 
same, but the resistance at the points of reversal is less with the horizontal 
two-pass baffling. 

Smoke records from a boiler baffled vertically and later changed over 
to horizontal baffling are shown in Fig. 6. The vertical baffles were re- 
sponsible for a high percentage of smoke, while with the horizontal baffles 
the boiler had a clean record. 



oz 


3 I 


BZ 


7 2 


5 Z 


5 2 


Mill I 


I 


9 1 


3 1 


1 r 


/ 1 


3 1 


S 1 


1 


1 


1 


K 


« 


I 




6 


1 


4 3 2 

1 1 


1T(\ 


- 


- 


- 


- 


- 


- 






- 


- 






- 




- 




- 


- 




- 




- 


- 


- 


- 




- 


- - 


' ^ T,n 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 






- 


- 


- 


- 




- 


- 




- 


- - 




- 


- 






- 


- 


- 


- 


- 






- 




- 


- 


- 


- 


- 




- 


- 




- 




- 


- 


- 


- - 




r> 


^ „l„l„j 


„ „ 


^1^ l„ 


■ ^ 


/// 


^ 


^ 


Y/y 


VAc 


V^/jy 


^d'Ki- 


~-' ^ 


z/:^'/z',^:m:^4^'^ -^-i^^ 1 


E10' 


^--, ~^~-^~-^ -^ „ _(^^~ 


1^ 


- 


— 4fll30 


~, 


- - 




— ,- „- 


~ 


- 


— 


T, - r- -\~ 




W-<\v\ 


- 


- 


- 






, 




- 1 - 


- 


- 


- 


- 


— 


- 


- 


- , 


- 


- 


- 




- 


- 


- 


- 


- 




- 


- 


- 


- 


- 


- 


- - 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 


- 


- 


- 


- 


- - 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


-\- 


- 


J 1 M) 


59 58 57 56 55 54 53 52 51 50 49 4S 47 46 45 44 45 dZ 41 40 39 3 


83 


7l6~5'5l4 Blz"3l^30+'"' | 























Vert 


ical 




Ba 


ffle 






















02 


9 2 


8 27 2 


6 2 


5 2 


U 


u 


2 Z 


20 19 1 

1 


3 1 


7 1 


3 1 


5 1 


1 13 12 1 


1 


] ? 


I 


" 


e 




" i 






8 -,7/1 1 


- 


- 


- 


- 


_ 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 




- 


- 


- 


- 




- 


- 


- 






- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




" c;^0 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 


- 




- 


- 


- 


- 


- 




— 


- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


^ ■^ ^n 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 




- 


- 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


~ 


— 




I" 


~ 


-? 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




- 




— 


— 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 




- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


^1030 


- 


- 


- 


'- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


— 


- 


- 




— 


- 


- 


— 


— 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 


- 




' t m 


59 58 57 56 55 54 S3 52 51 50 49 48 47 46 45 44 43 4 


Z~4J"40"3'9"58"J7"36'3S"34l3"j2~5l''30 ^'"^ | 



Horizontal Baffle. 
Fig. 6. Smoke Charts. 

Vertical baffles can be kept tight only with difficulty. Baffles that are 
not gas-tight allow the hot gases of combustion to short-circuit, resulting 
in high stack temperatures and a reduction in boiler efficiency. Because 
of the difficulty in installing the tiles, vertical baffles are often repaired 
with ordinary fire clay. With vertical baffling soot cleaning is difficult 
and the installation expensive. Frequently the cleaner is built in as a part 
of the baffles ; when the tile crumble away both the soot cleaner and the 
baffle must be renewed. 

According to the requirements, the horizontal baffles can be arranged 
for single, double, or triple gas-passes. Typical arrangements are shown 
in Chapter 4. The horizontal passes allow the gas to travel in series, 
in parallel, or for the two combined. The gases flow parallel to the tubes, 
as well as at right angles, when the pass is divided. The first baffle. Fig. 
8, is then placed on the lowest row of tubes and extends to within 5 ft. 
of the rear waterleg. This baffle serves as a roof for the furnace and 
combustion chamber and permits of a simple stoker arrangement, with 
ample room for the gases to burn. The gases entering the boiler divide 
into two streams, one flowing beneath and the other above the middle baffle. 



66 



BOIL 



This rests upon the ninth row of tubes, with an opening at both front and 
rear. The top baffle extends from the rear waterlec to within several feet 
of the front waterleg, leaving an opening fir :' t iisrnarge of the gases 
from the boiler tnbes. Before passing tc zlt sir -it outlet, all the gases 

flow under the ':;i'-er i: i.s. 

rials, desizzzi ::r t^r :::5:i i: i: i :: :: f: : :_ t : ^ t : zrivrt^. 
Theshs:r5 fti :r. iirrtrt;: fr:: ::;5 i-.n sJ: :; r^ . 5 :-iron plates 

are sonie: iizi .iti :;r :::e ;r::tr ^t: ;: : :-:^r3 ' :r i :. £les. 



Capacity and Economy 

device has its own type of characteristic carve in 

tref £5 iri'/ites against onfpnt as abscissas. This 

r 2. E:t?.: - liler resembles the carve for a steam 

■- e'e: :::: : ::;r :r generator, in being convex upward 

r.ri : :.-': ::; 1 peak. With all these devices, the 

a: . -:/: : if ifses absorbing the oatpat). Their 

~ir r; :.: :..::::~.— !!?2ds and at heavy overloads. 

- :.; itr-ti : : :r.jni loads depending upon 

It 1 1: t : r^r T L :': for a short time. Over- 

t- : r : _ -t :::-tr is si milar in maintaining 

5.::t: :r ::. :5 : : /.ry to carry overloads. It has 

_: ;::- :c ,ir.ve:- i: itfriTely by incre^?::^? the draft. 

: ':-.'.-: :i:\ :irr- yr::: im. load 



Every mechanical 
which efficiency is pic 
characteristic carve fc 
engine or turbine, or £i 
and having a wdl de£ 
efficiency falls to ztr: 
characteristic curve; ::: 
Electrical machiner 
ten^erature. A given 
loads do not reduce the 
efficiency, but is grea:! 
no definite time limit, : 
Except under extreir: 
indefinitely- 

With economical operaiicz sieam engines and tur^i^'ne? of the constant 
speed type have only moderate maximum overlrai ; ; . : The efficiency 
under overload drops off more rapidly than Lh^i oi a _:.ler. To obtain 
high overload capacity by admitting live steam to low presstire cylinders 
or stages leads to an abrupt drop of the effiaency, and even then there 
is a definite limit of capacity. The steam boiler, therefore, is almost tmiqne 
in its advantaeezus cer::r~ir.:e. 



iiuons 



Water Circulatioii 



In many heat-trar; 
as the fluid velocities i 
leads to rapid replace: 
the emission side, cc ; 
emitting fluid is other . 
difi^erence. In a stearr. 
points usually differ :: 
scarcely vary much wi: 
any mariced degree dej^ 
occurs by radiation, at 
marked degree depen i 
lion is sufficient to kee; 
by radiation, at surfaces 
gas circulation. 

Good drc^i' 
from difference 5 : : :. : 

mud in pockets 1 
of adhesive bv. - : 

local overheat:::^ T -! :.:z : 
liberating surface and poor cir 



C • ' C -N 



-- — - r uiiivi. j \^ on 

: .- rlui if the heat- 

eace to augmec: zi t :: perature 

water tempera:, rt 5 .-: vzrious 

mtity of heat : : : r : t : : ; i can 

\ ' the efficier ; i t5 : : ::: 

::. The hea: \::\,:z: \: ;i: 

■.jie fire, does not in any 

: i^aing that the drcula- 

- T -insfer which occtu-s 

i-c ^re, ^i'-es not depend upon 



.: ever. It reduces stresses arising 

-: -:r^? the acctunulation of scale or 

z :ends to prevent the formation 

-z s-rc:?. Such unwetted spots may cause 

: apt to exist when boilers with insufficient 

culation are driven hard. 



BOILERS 



67 



Steadiness of Water Level 

This implies a large water surface "disengaging" or "liberating" surface, 
in proportion to the volume of water ; or perhaps more strictly, in proportion 
to the expected total evaporation. Priming may result from inadequate 
liberating surface and occurs, consequently, in many vertical boilers having 
the water level below the tops of the tubes. Drums should not be too small, 
else slight variations of water level may carry it rapidly below the danger 
line. 






B-Tile. T-Tile. L-Tile. 

Fig. 7. Forms of Tile Used with Heine Boilers. 







.... . ..r . ... . ...<..r ■■■■.. . ... . . . . . . . ■_■■■ ■■■ . . n . 1- 

\'o 'o '.'^. > ■ ■' •■ » J'" >■ .3 ;>■ • •..-.• 







Fig. 8. Divided Pass Baffle in Heine Boiler. 




Railway Exchange Building, St. Louis, Mo., operating 
1052 H. P. of Heine Standard Boilers. 



69 



CHAPTER 3 



SUPERHEATERS 

SUPERHEATED steam is steam whose temperature is higher than that 
corresponding to saturated steam at the same pressure ; steam which, when 
heat is removed, will not immediately begin the process of condensation. 
The properties of superheated steam approximate those of a perfect gas. 
Tables of these properties are given in Chapter 12 on STEAM. 

Advantages of Superheating. These are important because superheating 
reduces pipe and cylinder condensation. In a well-designed attached super- 
heater, the efficiency of the heating surface is at least as high as that of 
the boiler; and as the total heating surface is increased by that of the 
superheater the exit temperature of the gases will be decreased. This in- 
creases the overall efficiency of the boiler and superheater to a point which 
will, in general, make up for the increased heat required by the steam. With 
an independently fired superheater, more fuel will, of course, have to be 
burned. 

The measure of the extra fuel for superheating is the difference in 
the total heat of the steam when saturated, and when superheated ; this will 
depend upon the pressure and the superheat temperature, and also upon the 
temperature of the feed water. The following figures are based on a gage 
pressure of 165 pounds : 



Amount of 


Extra fuel, per cent, required when feed water enters at 


Superheat, 
Degrees 


100° 


150° 


212° 


50 
100 
150 
200 


2:73 
5.13 
7.40 
9.61 


2.85 

5.38 

7.74 

10.05 


3.03 

5.70 

8.21 

10.66 



The superheater does some of the work which the heating surface of 
the boiler would have to do if the same number of heat units were to be 
supplied in saturated steam, so that the boilers can be run at lower rating. 
The superheater may not increase the first cost of the boiler plant, for 
with the increased economy the number of units used may be decreased. The 
increased economy of the engines due to the use of superheated steam may 
naturally enable smaller condensers to be used, and may lessen the cost of 
pumping owing to less water being used. Superheated steam is used, almost 
without exception, in the largest and most economical plants. 

The pipe radiating surface can be reduced by the use of smaller pipes, 
owing to the fact that higher velocities (as high as 12,000 ft. per min.) are 
permitted with superheated steam. 

The theoretical gain is indicated in the temperature-entropy diagram, 
Fig. 9, in which areas represent heat quantities. The line (oa) starting at 
a temperature of 32 deg. is the liquid line and the area under (oa) represents 
the heat of the liquid, q, that is, the heat necessary to raise the temperature 
of one pound of water from 32 deg. to the temperature corresponding to 



70 







V 

o 

■4-1 

CO 



3^ 



a; 



O 
o ^ 



^2 



1(3 

o 
to 

c 



PQ 

u >* 

CO u 

cW 

w c 

C o 

^ CO 



o 
o 

CO 



SUPERHEATERS 



n 



the pressure in the boiler where the vaporization takes place. The line (ab) 
represents this process of vaporization and the area under it is the heat, L, 
added during the process. At (b) the steam is in a dry-saturated condi- 
tion: (be) shows the superheating of the steam at constant pressure and the 
area below is the heat added during the process. The steep slope of the 
line (be) shows that the point (c), which is the final condition of super- 
heat, must be carried to a high temperature in order to have the area below 

\T 




1 / h 



Ir 



i\\\\\\N\\\\\^\\\\^/////////^^^^^ 



'/A 



Fig. 9. Temperature — Entropy Diagram. 

of any size. A high degree of superheat, which means a high temperature, 
will add only a small number of heat units to the dry-saturated steam. 

For example, dry steam at 150 lb. abs. pressure has a heat content of 
1195 B. t. u. per pound. If this steam is superheated 141.5 deg. to a tem- 
perature of 500 deg., the heat content will be 1274 B. t. u. or a gain of only 
79 B. t. u. per pound for an increase in temperature of 141.5 deg. ; or 6.6 
per cent increase in heat for 39.5 per cent gain in temperature. 

Effect on Reciprocating Engines. Steam, admitted to the cylinder of 
an engine, comes in contact with walls that have been cooled by contact 
with the low pressure steam exhausted during the previous stroke. Heat 
flows, therefore, from the steam to the cylinder walls, and if the steam is 
saturated part of it will be condensed ; sometimes this will be as much as 
20 or 30 per cent. The loss due to surface condensation is one of the most 
serious occurring in the reciprocating steam engine. If the steam entering 
the cylinder is superheated, then the flow of heat caused by contact with the 
colder cylinder walls will cause a decrease in the amount of superheat, but no 
condensation until the temperature has been reduced to that of saturated 
steam. 

The many tests made on reciprocating engines using saturated and 
superheated steam have shown a smaller steam consumption for superheated 
steam. With moderate amounts of superheat, that is, up to 200 deg., the 
gains have been greater than for the higher temperatures. The extra invest- 



u 



SUPERHEATERS 



ment and cost of maintenance neutralize the gain from the higher temper- 
atures. The gain in steam economy due to superheat is most striking with 
small, simple engines, in which the cylinder condensation losses are the 
greatest. 

Tests on Buckej-e engines (simple 12 by 16 in., and compound 10 and V/Vz 
by 16 in.) with steam at 100 to 110 lb. pressure, show about what can be 
expected in this wav. Table 3 gives results of tests with superheats up to 
200 de.g. 



Table 3. Pounds of Steam Per H. P. Per Hour for Different Superheats. 



! 

_, . Rated load. 


Superheat temperature, degrees 


Engine Percent 


50 100 150 200 


Simple, non-condensing 

Simple, non-condensing 

Simple, non-condensing 

Com.pound, non-condensing. . . . 
Compound, condensing 


30 

50 

100 
100 
100 


-35.0 

31.5 
28.5 


28.0 

25.5 
24.0 


24.0 

22.0 
20.0 
17.5 
14.0 


21.5 
19.0 
18.0 
15.5 
12.5 


19.5 
17.5 
17.5 
14.6 


18.0 


16.5 


11.5 



G. F. Gebhardt states that a fair estimate of the average percentage reduc- 
tion in steam consumption per horsepower hour with moderate superheating, 
that is from 100 to 125 deg.. based on continuous operation of existing 
plants, is : 

1. Slow running, full stroke or throttling engines, including 

direct-acting pumps 40 

2. Simple engines, non-condensing, with medium piston speed, 

including compound, direct-acting pumps .20 

3. Compound condensing Corliss engines 10 

4. Triple expansion engines 6 

European builders guarantee steam consumption (in lb. per LH.P. per 
hr.) with highly superheated steam (total temperatures 750 to 850 deg.) 
as follows : 

Single cylinder condensing engines (uniflow) 8.5 

Single cylinder non-condensing engines (uniflow)... 12.0 

Compound condensing engines (locomobile) 8.0 

Compound non-condensing engines (locomobile) 10.5 

W. E. Dalby gives results on a small engine using superheated steam, 
taking the data from tests by Professor Ripper. Table 4 shows the differ- 
ence in the increase of the efficiency of theoretical and actual engines, both 
working under the same conditions : 

The steam is drj'-saturated in the first case. The theoretical efficiency 
increases from 14.2 to 15.9 per cent, or 11.6 per cent, while the actual 
efficienc}- gains 65.0 per cent, the increase being from 6.3 to 10.4 per cent. 
This shows, of course, that the superheat acts to decrease the losses in the 
actual engine. 

In comparing the performances of different engines, the heat consump- 
tion, rather than the steam consumption, should be used. The number of 
heat units required to develop one indicated horsepower in the actual engine 
takes into consideration the pressure, superheat and the steam consumption 
ihe avoidance of cylinder condensation by the use of superheat will affect 
both heat and steam consumption. So whatever the basis of comparison, the 
employment of superheated steam is an advantage. 



SUPERHEATERS 



73 



Table 4. Effect of Superheat on Actual and Theoretical Engines. 





Steam 

pressure, 

Lb./Sq. In. 


Superheat 
Degrees 


Steam 
Lb ./I. H.P./hr. 


Thermal efficiency, per cent 


I. H. p. 


Act. eng. 


Theor. eng. 


13.33 
13.33 
13.47 
13.49 


101.7 

98.5 
98.6 
99.5 


0.0 

98.3 

254.2 

319.6 


39.62 
33.80 
23.36 
20.08 


6.3 

7.1 

9.5 

10.4 


14.2 
14.6 
15.2 
15.9 



Effect on Steam Turbines. The theoretical gain from the use of super- 
heated steam is the same in steam turbines and in reciprocating engines ; 
in either the available number of heat units are increased by the use of the 
superheating process. The actual gain, however, is less in the turbine than 
in the engine, for the action of the steam in the former is continuous while 
in the latter it is intermittent. Superheated steam is of little value in cor- 
recting surface condensation, because practically none occurs in the turbine. 

The water rate of the turbine is decreased by the superheating of the 
steam but to a less extent than in the reciprocating engine. Superheating is 
of importance in that erosion of the turbine blades caused by the presence 
of water in the saturated steam is almost entirely done away with. 

The effect of expansion on saturated steam is to increase its moisture 
content, so that even if the steam were dry at entrance, moisture would be 
present in the low pressure stages. If the steam is sufficiently superheated 
the heat reduction due to the expansion will not lower the temperature to 
that of saturated steam, which must be reached before condensation begins. 
Any moisture present in saturated steam has the effect of reducing the 
economy. 

The steam consumption of certain large turbines using superheated steam 
is decreased about 1 per cent for every 8 to 12 deg. of superheat up to 200 
deg. ; the variation being from about 1% for 12 deg. at 50 deg. superheat to 
8 deg. at 200 deg. superheat. In the same boiler plant the minimum saving in 
coal due to superheating is 4 to 5 per cent. This coal saving depends upon 
(1) the saving of steam resulting from the economy of the prime mover; 
and (2) the amount of coal necessary to obtain the superheat. 

Limit of Superheat. As far as material goes power plant apparatus 
might be designed to withstand temperatures of 800 or even 1000 deg. 
Other considerations, however, limit the amount of superheat, so that the 
most economical degree is determined by the operating conditions. 

In this country steam temperatures in power plants are seldom more than 
600 deg. ; the superheat is from 200 to 250 deg., depending upon the boiler 
pressure. In Europe, however, where superheaters are almost invariably 
employed, 600 deg. is a common temperature and 400 deg. superheat, which 
would be a temperature of about 850 deg., is sometimes used. 

With these very high temperatures the first cost and maintenance are 
high, and the thermal gain is considerable. This would be advantageous 
when materials and labor costs are reasonable and fuel costs high. Such 
conditions were formerly found in Europe. In this country, however, labor 
and materials are expensive while fuel has been cheap. It is more economical, 
therefore, to use moderate degrees of superheat, even at the sacrifice of 
some gain in heat ; but as the cost of fuel increases, the tendency will be 
towards increased superheat. 

The engine design also determines to some extent the temperature to be 
used. The Corliss and slide-valve types of engines seem to reach their limit 



74 




SUPERHEATERS 75 



at about 500 deg. Higher temperatures cause warping of the valves and 
interfere with lubrication. 

Very highly superheated steam, at temperatures of 600 deg. or more, 
is used in poppet-valve engines, since such valves do not warp and require 
no lubrication. Balanced piston and specially designed Corliss valves are 
also successful with high superheats. 

Steam-turbine construction and operation permit the use of steam tem- 
peratures as high as 800 deg. Nevertheless for reasons of economy of main- 
tenance, even the latest designed turbine plants are working with steam at 
temperatures not over 650 deg. 

Control of Superheat. Superheat temperatures may vary widely with 
the temperature of furnace, volume of air used, and rate of firing coal. 
Extreme variations should be avoided, as they may cause serious difficulties 
with the piping, valves and gaskets. Stoker firing and automatic feed and 
damper regulation will do much toward eliminating superheat fluctuations. 

Any variation in the boiler load will affect to a marked degree the tem- 
perature in superheaters placed inside the boiler setting, in the path of the 
hot gases. The truth of this last statement is shown by Fig. 10, and by the 
following quotation from "Superheater Logic," by the Heine Safety Boiler 
Company : 

"If the increase in load is sudden and there is a large momentary draft 
of steam with accompanying fall in boiler pressure, the superheat tempera- 
ture will fall because the rate of combustion is not increased. Conversely 
if a boiler is steaming at a heavy load and the load decreases suddenly, then 
the superheat, which is already very high due to the heavy load, will be 
further increased because of the smaller flow of steam through the tubes. In 
this way very excessive superheats are obtained from an equipment designed 
for only a moderate superheat at normal load. 

"Evidently the greatest economy is secured when a plant is designed 
and built for a certain fixed superheat and this temperature is maintained 
constant." 

Types of Superheaters. In general use are (1) the separately-fired, 
and (2) the attached type of superheater. The former is placed in its own 
setting and has a furnace of its own to supply heat; the latter is located 
within the setting of the boiler and receives heat from the hot gases as they 
pass on toward the stack. Both types receive steam containing perhaps 2 
per cent moisture from the boiler and increase its temperature by the addi- 
tion of heat without changing the pressure. The steam elements are prac- 
tically the same in both types — a number of tubes or pipes arranged to contain 
a relatively small volume but to expose a large surface to the heat. 

The final temperature of steam in a superheater depends upon the tem- 
perature, volume and quality of the steam entering it, and upon the volume 
and temperature of the hot gases coming in contact with the tubes. The 
temperature and quality of the steam can be considered as constant while 
the load on the boiler determines the quantity of steam. Therefore the 
amount of superheat will be principally affected by the temperature and 
volume of the hot gases. If it is desired to maintain a constant degree of 
superheat, the flow of hot gases over the tubes must be controlled. 

Separately-fired superheaters are intended to give higher temperatures 
to the steam than can be obtained from attached superheaters. The super- 
heating coil is suspended over the furnace, protected from the direct heat 
of the furnace. Baffles are provided so that the hot gases make two or more 
passes around the tubes. Steam enters at the top and leaves at the bottom. 
The tube surface is increased by putting on cast iron rings outside the tubes. 

A flow of steam through the superheater must be provided to prevent 
burning, should the load be suddenly thrown off the boiler. All super- 
heaters should be equipped therefore with independent safety valves of the 



76 



SUPERHEATERS 



outside spring type, set at a slightly lower pressure than the boiler safety 
valves. There should be a drain for getting rid of any collected water 
before starting. The superheater should be so proportioned that the same 
quantity of steam will pass through all of the tubes in order that none of 
these can be by-passed, and consequently in danger of burning. 

Superheaters must be protected from exposure to hot gases with no 
steam flowing, as when firing up, cooling down or standing idle. With 
separately-fired superheaters the hot gases can be deflected so as to by-pass 
the superheating coil and flow directly from the furnace to the stack; 
or an outer cast iron covering with flanges may be provided to protect 
the steel tubes and store the heat. Also the superheater should be filled with 
water, or flooded whenever the flow of steam ceases. Flooding is objectionable 
in that scale-forming material can be deposited in the tubes, which cannot 
be cleaned. 

Any of the above methods may be applied to attached superheaters. 
When these are flooded the)^ generally are connected in parallel with the boiler 
heating or evaporating surface, so that they can be drained and connected 
in series with the boiler when superheat is desired. 

The attached or indirectly-fired superheater may be placed (1) at the 
rear of the furnace; (2) at the end of the heating surface just before the 
gases leave the boiler setting; and (3) at some intermediate point. 

The steam passing through the superheater will absorb heat, depending 
upon the temperature difference between the gases and the steam, and upon 
the amount of superheating surface. Therefore to obtain the same degree of 
superheat the amount of surface required in the furnace where the gases 
are hottest may be small as compared with the amount required when the 
superheater is placed at the end of the heating surface, where the gases are 
cooler. The usual location of the superheater in the boiler setting is such that 
the temperature of the hot gases reaching it seldom exceeds 1500 deg. In 
this position the attached superheater is subjected to the fluctuating tempera- 
tures of the hot gases. The amount of superheat will vary, therefore, with 
the load on the boiler and will increase as the boiler is forced. 



1 U V 

160 
S 140 

JZ 
L. 

§-120 
to 

1 '°° 

1 80 

g 60 
o 

I 40 

20 












































^ 




















^ 


















^ 


^ 


















,y 


^ 




















/ 


/ 






















/ 







































































so 



100 



ISO 



200 



250 



ZOO 



Percen+ Looid 

Fig. 10. Effect of Load on Superheat with the Superheater in the 
Path of All the Boiler Gases. 



SUPERHEATERS 



n 



The more positive method of maintaining a constant superheat is by 
locating elements in a separate chamber, where a damper can be used to 
regulate the flow of gases, automatically if desired. The superheater can 
then be by-passed altogether in an emergency. 

Figs. 11 and 12 illustrate the details and location of the Heine super- 
heater. This consists of two parts, the superheater box and the tubes. Into 
this box are expanded the steel tubes arranged in four passes as shown. 
Two interior partitions separate the superheater box into three chambers. 
The steam enters at the bottom, passes through the lower tubes, returns to 
the central chamber through the second pass tubes and then flows through 
the third and fourth passes, returning to the upper chamber. 




3 L 

1 C 




Fig. 11. Details of Heine Superheater 
The location of the superheater is shown in Fig, 12. It can be installed 
on one or both sides of the boiler, according to the boiler size, and the 
superheat desired. The entire superheater is encased in brick work with 
a firebrick roof supported by special T-bars. This superheater chamber 
communicates with the furnace by a flue formed in the side wall, through 
which a small part of the furnace gas rises. This gas enters the rear of 
the chamber, makes two passes over the tubes and leaves at the front of the 
setting, passing over the surface of the boiler drum. A damper in the 
chamber outlet controls the flow of hot gas and is regulated from the front 
of the boiler, either by hand or by an automatic temperature control. 



78 



SUPERHEATERS 



Obvioush', the temperature of the superheated steam can be changed 
as desired by simplj- manipulating the damper in the outlet of the super- 
heater chamber, and the superheat can be maintained constant, regardless of 
the boiler load, the rate of combustion, the amount of air used for combus- 
tion, the furnace temperature, the opening of furnace doors or any other 
variable, such as the amount of soot on boiler and superheater surface. 




Fig. 12. The Heine Superheater. 

For automatic regulation of the superheat temperature, a complete regu- 
lator is installed as shown in Fig. 13. This regulator is quick acting and 
responds to small variations in steam temperature, as will be evident from 
its construction. 

The entire device consists of two main parts, the controller and the 
diaphragm-motor. The controller comprises a thermostat which con- 
trols a small supply of compressed air in accordance with the temperature of 
the superheated steam. The air is admitted to or released from the 
diaphragm-motor, connected by a link to the superheater damper handle. 

Provision for soot blowing is described on pages 31 and 41. 



SUPERHEATERS 



79 



Superhea-f-ed Steam Li'ne •■' 




Damper Pod'' 



Fig. 13. Arrangement of Automatic Temperature Regulator 
with Heine Superheater. 

The requirements of a successful superheater, as given by Gchhardt, are : 

1. Security of operation or minimum danger of overheating. 

2. Economical use of heat applied. 

3. Provision for free expansion. 

4. Disposition so that it may be cut out without interfering with the 
operation of the plant. 

5. Provision for keeping the tubes free from soot and scale. 

Superheating Surface. The surface required is dependent upon the 
amount of heat to be transferred to the steam, and upon the rate of heat 
transfer per unit of surface. The operation is conveniently divided into three 
stages : 




Fig. 14. Superheat Chart from a Boiler Equipped with a Heine 
Superheater and Automatic Superheat Controller. 




o 



C 
& 

CO 

V 

c 

'v 

X 



T3 
V 

a 
o. 

'5 

V 

6^ 
"o 
U 

1) 

> 

G 

V 

Q 

"o 
o 

u 

£ 

V 

j: 

U 

O 



SUPERHEATERS 81 



1. Heat given up by the gases. 

2. Heat transmitted through the metal walls of the elements. 

3. Heat absorbed by the steam. 

The amount of heat involved in each of these stages is the same except 
for loss by radiation. 

The heat given up by the gases is : 

Wc (h—U) (4) 

the heat transferred is : 

SRd (5) 

and the heat absorbed bv the steam is : 

Wct {t,—h) (6) 

where : 

^'^Superheating surface, sq. ft. per B.H.P. 

J'?=B.t.u. transferred per hour per sq. ft. of superheating surface 
per deg. F difference betw^een the mean temperatures of the 
gases and of the steam, and approximates : 

1 to 3 for superheaters located at the end of the boiler 

heating surface, 

3 to 5 when located between the first and second passes, 

8 to 12 for separately fired superheaters and for superheaters 

located immediately over the furnace in stationary 

boilers or in the smoke box of locomotive boilers. 

rfrndifference between the mean temperatures of the gases and steam. 

W^=we\ght of gases passing through the superheater, lbs. per B.H.P. 

per hour, 
w^weight of steam passing through the superheater, lbs. per B.H.P. 

per hour. 
ci:=mean specific heat of the gases, 
c^nzmean specific heat of superheated steam. 
fi=rTemperature of gases entering superheater, deg. F. 
^a^Temperature of gases leaving superheater, deg. F. 
^3=Temperature of superheated steam, deg. F. 
^4=Temperature of saturated steam, deg. F. 

Neglecting radiation, (1) is equal to (2) ; and neglecting the moisture 
in the incoming steam, (2) is equal to (3), therefore : 



and 



S: 



Rd (7) 



'R^ (8) 

Instead of (3), the following may be preferred: 

w (H^—I-h) (9) 

where : 

FI^=Tota.\ heat of superheated steam above 32 deg. F. 
jF/2=Total heat of saturated steam above 32 deg. F., which may be 
easily corrected to allow for evaporating the moisture present. 

Instead of basing R on the difference in the temperatures of the gases 
and of the steam, it is more correct to divide the heat transfer into two 
stages— gas to metal and metal to steam. As this necessitates a knowledge 
of the metal temperatures it is generally confined to laboratory research. 
The precise value of R is dependent upon so many variable conditions, such 
as the velocity of the gases and of the steam, the condition of the surfaces 
as to soot and scale, the arrangement of the superheater tubes and the 
temperature differences involved, that refinements are out of place. I he 



SUPERHEATERS 83 



amount of surface Is usually determined empirically on formulae derived 
from the results obtained in a large number of cases of the same general 
design, operating under similar conditions. This leaves the result in con- 
siderable doubt where the whole of the gases flow over the superheater 
with no possible control. With only a part of the gases flowing over the 
superheater under perfect control, the amount of surface can be simply 
related to the boiler heating surface, according to the degree of superheat 
required, and the resulting steam temperature will be kept constant within 
±: 5 deg. F., as shown in Fig. 14. 

Superheater Materials. Heire superheaters are built of wrought steel, 
insuring ease of construction and durability. 

Superheater Piping and Fittings. Cast iron has been used for valves and 
fittings. Up to 600 deg., it is safe if the temperature is maintained constant. 
Under higher or fluctuating temperatures permanent increase in dimensions 
and numerous failures have resulted. Cast iron failures are undoubtedly due 
more to fluctuations in temperature than to constant high temperatures when it 
develops cracks and distortions. 

The advantage of cast steel for superheater material is that it is not 
damaged at high temperatures. This decreases the importance of protection 
and simplifies the installation. The construction, however, must be heavy 
and thick-walled. 

The strength of superheater materials drops off rapidly for temperatures 
above 600 deg., as shown by Gebhardt and others. Because of this rapid 
decrease in tensile strength, steam is seldom superheated to temperatures 
above 850 deg. 

Piping for superheated steam is usually made of mild steel. With the 
greater number of heat units in superheated steam, the pipe capacity is 
increased and relative conduction losses and leakage are reduced. Under 
superheated conditions much higher steam velocities can be used, 12,000 ft. 
per min. not being uncommon and 16,000 ft. per min. having been used. 
This, of course, increases the pipe line capacity. With the high tempera- 
tures resulting from superheat the problem of expansion must be carefully 
considered, especially when temperatures are likely to fluctuate widely. See 
chapter on piping. 

Industrial Uses. Superheated steam is used elsewhere than in engines 
and turbines. A Chicago gas company blows its water gas generators with 
superheated exhaust steam at about 2.5 lb. pressure, instead of using live 
steam. This results in a 20 per cent saving of boiler fuel. The capacity of 
the generators is increased because of the lengthening of the making period. 
The superheated steam relieves the generator of the work of re-evaporating 
the water, which is always present when saturated steam is used. 

Superheated steam is successfully used for process work, where both 
the latent heat and the heat of the superheat of the steam can be used, as for 
example, when the steam can be blown directly into the substance to be 
heated. When, however, only the heat of the superheat can be employed, 
the use of superheated steam does not pay. Its specific heat is only about 
one-half that of saturated steam and therefore, about twice as much super- 
heated steam would be required. Superheated steam may be justified when 
the heat of the superheat can be used in one operation and the latent heat 
or part of it in a connecting operation. The saturated steam left after the 
first operation must then contain enough heat for the second operation. 



84 




> 

(3 



Ul 



73 



C3 

ID « 

u 

u 









S = 



> . — 



r = 3 

^- = > 

1< - 

^ ,9 'Z 



Z> 2 

- 3 



v. — 



o 






85 



CHAPTER 4 



FURNACES AND SETTINGS 

PROPER furnace design and adequate proportions are the essentials in 
securing high boiler efficiency. A single design of setting cannot be 
standardized to meet the various fuel, operation and space requirements. 
To obtain complete combustion, special designs are required for low and high 
volatile coals, gas, fuel oil, waste heat, and for hand or stoker firing. 

Furnace Design 

THE main problem in furnace design is to determine the volume of the 
furnace and the length of the flame travel. Furnaces with a small com- 
bustion space, in which the flame travel must be short, are not suited for the 
burning of high volatile coals at high rates of combustion. For reasonably 
complete combustion, the combustion chamber must be large enough to permit 
thorough mixing of the air and gases; sufficient time for combustion; and to 
maintain temperature sufficiently high to secure combustion. 

Mixing. To secure efficient combustion, the volatile distilled from coal, 
which in part is composed of tar vapor, gases and small solid particles of 
floating carbon, must be intimately mixed with an adequate supply of air. Fuel 
oil and gas must also be mixed thoroughly with air. If the right mixture is 
not maintained, the result is stratification, such as is common in hand-fired 
furnaces not operated properly. In stoker-fired installations the fuel is more 
evenly distributed over the grate. This prevents the inrush of large quantities 
of air in spots and the choking of air in other parts ; the products of com- 
bustion are, therefore, mixed more uniformly with oxygen-bearing air. 

Additional air is sometimes supplied above the fuel bed to obtain thor- 
ough burning. Arches, piers, wing walls and steam jets are sometimes added 
in hand-fired furnaces to give a thorough mixture of air and gas so that the 
higher volatile coals can be burned without smoke. The locations of these 
parts depend upon the kind of coal and the manner in which the boiler 
is to be operated. Such structures increase the draft loss through the boiler, 
so that the steaming capacity for a given draft is reduced. Generally, how- 
ever, they improve' combustion. 

Time. This is next in importance to the mixing requirement. The time 
available for combustion (before the gases are cooled by the boiler heating 
surface) depends upon the length of gas travel, or for the same grate area, 
upon the cubical contents of the furnace. The combustion space must be 
correctly related to the rate of combustion for a given fuel, otherwise economy 
will be sacrificed. 

Experiments by the Bureau of Mines with a Heine Boiler indicate the 
relation between boiler economy and furnace volume, as in Fig. 15. In 
these, semi-bituminous coal was burned on a Murphy stoker having a pro- 
jected grate area of 25 square feet. Pocahontas steaming coal was con- 
sumed at the rate of 65.4 lb. per sq. ft. of grate per hour. When the 
products of combustion had passed through 80 cu. ft. of combustion space, 
the gases contained fully 2).7 per cent of unconsumed combustible, but as 
the space traversed increased to 160 cu. ft. the combustible decreased to 
1 per cent When a point corresponding to 260 cu. ft. of the furnace volume 
had been passed less than 0.5 per cent of combustible remained in the 
gases. This indicates that the larger the combustion space, the more nearly 
complete is combustion. 



86 



F I' R X A C E S A X D S E T T I X G S 



to 


1 ' ' ' ^ ' 1 1 I 1 1 I 1 1 1 1 ' ' ! . ' 1 I 


9 


1 






1 


i , . , - : . 






! 


I'll 


8 












\ 




1 










1 














\ 




1 










1 




t7 










\ 










\ 


26 






1 


' \ 














1 


\ 








i 


o _ 


\ 
















1 


c ' 
O 

£ 4 


\ 


































\ 










































> 


1 


























^3 


















\ 












































s. 






















1 


o 








1 












s, 




















i I 


' 








s 




























V 




^ 
































' - 


n 


1 






















' ■ ■ . \~ 



5: 



100 153 200 

Combustion Space Volume, Cubic Feet 



250 



300 



Fig. 1 5. Relation between Furnace Volume and 
Completeness of Combustion. 



Temperature. The combustible gases in a boiler furnace must be 
kept at a temperature sufficiently high to permit complete combustion, 
economically and without smoke. The ignition temperature of hydrocarbon 
gases is between 1000 and 1500 degrees. However, this temperature varies 
with the amount of air, kind of fuel, and the quantity of neutral gases present. 

A high furnace temperature generally means rapid combustion and good 
efficienc}-. It is the result of higher CO2 and the absence of CO, so that 
the gases are more nearly burnt while traversing the furnace. The varia- 
tion of furnace temperature and boiler load is shown in Fig. 16. which 
represents tests by the U. S. Geological Sun-ey on a Heine boiler and 
underfeed stoker. 



3000 

2800 

2600 

52400 

^2200 

I. 

o2000 
II. 

• 1800 
|l600 
O1400 
^1200 
£1000 
I 800 

H 60ot 

i 400 

c 

= 200 









1 




































































_^ 


































'-' 


























^ 


^ 
























^.^-^^ 














1 










^ 
































> 


^ 
































/ 


/ 




1 












! 




/ 




































/ 

/ 




































1 


/ 
























1 

1 






































1 


































1 






































i 1 1 



20 



40 



60 



80 ;C0 120 140 

Boiler Capacity, Percent 



160 



ISO 



200 



Fig. 16. Relation Between Boiler Capacity and Temperature of 
Combustion Chamber. 



FURNACES AND SETTINGS 



87 



The effect of temperature is also shown by tests of the University of 
Illinois on a Eleine boiler equipped with a Green chain grate, Fig. 17. An 
economizer and a large induced draft fan were used, so that the rates of 
combustion were high. Coals having a combustible volatile content of 
from 30 to 40 per cent were successfully burned. Fire clay tiles are 
placed on the boiler tubes directly over the fire, forming the roof of the 
furnace and preventing the hot gases, which are still not fully mixed, from 
coming in contact with the cooler tubes. 



■»j/J"|*— J'-^^'-— >|/5"p 




Fig. 17. Heine Boiler Tested for Smokelessness. 



Tests were conducted on this boiler with C-tile on the bottom row of 
tubes, and then with 7'-tile. The C-tile encircle the tubes completely and 
present to the furnace a roof of solid firebrick. The T-tile rest upon the 
top of the tubes only, and therefore present to the furnace a roof of part brick 
and part water tubes. 

With T-tile, the smoke record varied from 9 to 17 per cent, which 
corresponds to Nos. ^ and 1 on the Ringelmann scale, respectively. The 
C-tile record showed zero smoke. The temperature of the gases entering 
the nest of tubes from the combustion chamber averaged 1384 deg. in the first 
test, and 1678 deg. in the second test. The corresponding temperatures 
over the bridge wall were about 1850 and 2150 degrees. 

Over 100 trials were made at loads varying from 60 to 150 per cent of 
rated boiler capacity, and from these L. P. Breckenridge concluded that it 
is almost impossible to make smoke with this setting under any condition 
and that it operates with economy. 

Furnace Volume. The Bureau of Mines shows that the furnace size is 
influenced mainly by the percentage of excess air, the rate of combustion and 
the kind of coal. 



FURNACES AND SETTINGS 



89 



A Heine boiler and a special Murphy side-feed stoker furnace were 
used in the tests. Table 5 gives the composition of the three grades of coal 
— Pocahontas, Pittsburgh and Illinois — ^burnt in these tests. The results, 
Fig. 18, represent a supply of 50 per cent excess air for two rates of com- 
bu'slion of the different coals, and give the combustion space necessary per 
square foot of grate area for various combustion conditions, which are 
expressed in terms of the ratio of undeveloped heat to the total heat in 
the coal. These figures can be used as a guide in proportioning almost any 
style of furnace. 




1.6 2 2.5 3 3.5 

Unconsumed Combustible, Percent. 

Fig. 18. Combustion Space Required per Square Foot of Grate Surface. 
Based on 50 Percent Excess Air for Coals Tested. 



90 



FURNACES AND SETTINGS 



Table 5. Analysis of Coals Used in the Tests. 
PROXIMATE ANALYSIS OF COAL AS RECEIVED 



Constituent 


Pocahontas 
Coal 


Pittsburgh 
Coal 


Illinois 
Coal 


Moisture 

Volatile matter 

Fixed carbon 

Ash 


per cent 

per cent 

per cent 

per cent 


2.21 

15.78 
71.65 
10.36 


2.51 

30.28 
56.82 
10.39 


16.16 
34.09 

39.19 
10.56 




100.00 


100.00 


100.00 



ULTIMATE ANALYSIS OF DRY COAL 



Hydrogen per cent 

Carbon per cent 

Nitrogen per cent 

Oxygen per cent 

Sulphur per cent 

Ash per cent 



Calorific value per pound, as received B. t. u. 



3.92 

80.90 

1.06 

2.97 

.56 

10.59 



100.00 



13,762 



4.82 
76.57 
1.55 
4.99 
1.41 
10.66 



100.00 



13,365 



4.66 
69.63 
1.49 
9.55 
2.08 
12.59 



100.00 



10,433 



A long narrow combustion space is to be favored rather than a short 
wide one of the same cubical contents. For conditions other than Murphy 
type furnaces the secondary air supply should be thoroughly mixed with 
the gases arising from the fuel-bed. The secondary air should always be 
admitted near and over the fuel-bed, at high velocity, and in a large number 
of streams. 

A variation of 50 to 100 per cent in the excess of air makes no appre- 
ciable difference in the efficiency of the small furnace. In a furnace of 
large size, however, a small variation in the excess air will affect the oper- 
ating efficiency, so that close control of the air supply becomes necessary 

The minimum percentage of unconsumed combustible in the products of 
combustion is much larger in a furnace having a small combustion space than 
in a furnace having a large combustion space. The efficiency obtained with 
the large combustion space is therefore much higher. For boilers operated at 
heavy overloads, a large furnace volume is particularly essential. 

Efficient combustion is secured when the furnace volume permits ample 
time, adequate mixing and sufficient temperature for thorough burning of 
the gases. The boiler settings should be high and the baffles placed horizon- 
tally on the tubes. The horizontal baffling promotes the mixing of strat- 
ified layers of the gases, and gives the gases time to burn completely before 
the tubes cool them below the temperature of ignition. 

Head Room for Coal Burning Boilers. A definite height of boiler setting 
is required for complete fuel combustion. Investigations by O. Monnett on 
settings for the smokeless combustion of soft coal are summarized in Table 
6, applying to water-tube boilers under average operation. 



FURNACES AND SETTINGS 



91 



Table 6. Headroom Requirements for Smokeless Settings 



Furnaces 



Horizontal Return 










Tubular 


Water Tube 










Hor. 


Vert. 


Hor. 


Vert. 


54 


60 


66 


72 


Eaflf. 


Baff. 


Baff. 


Baff. 










1-U' 


1-14" 


3i' 


8i' 










Pitch 


Pitch 


Pitch 


Pitch 



Continental 

or Scotch 

Marine 



(All Dimensions in Inches) 



No. 6 

-d No. 7 

.^No. 8 

'O Down draft 

03 McMillan 

•^ Twin fire 

Semi. ext. refuse 
burning 

•>^ Burke 

2 rJi McMillan.... 

Chain grate 

c 73 Moore 

2 oj Roney 

fe^ 20th Cent.... 

^ Detroit 

^-^ Model 

17)^ McKenzie. . . . 
Murphy 

ol T3 American 

"§ oj Jones 

Taylor 

Westinghouse 



Shell to dead plate Front header to floor 



32 


34 


34 


36 


72 


* 


78 


* 


36 


40 


40 


42 


t 


t 


t 


t 


32 


34 


34 


36 


72 


* 


78 


* 



Shell to floor 



60 


60 


60 


60 


72 


* 


78 


* 


52 


54 


60 


60 


72 


* 


78 


♦ 


58 


60 


62 


64 


72 


* 


78 


* 


ft 


ft 


tt 


tt 


84 


* 


90 


* 


48 


48 


50 


54 


60 


* 


66 


* 


48 


48 


50 


54 


60 


* 


66 


* 


72 


72 


78 


78 


84 


114 


96 


120 


48 


54 


60 


60 


72 


102 


78 


108 


60 


60 


60 


72 


84 


108 


90 


120 


54 


60 


66 


72 


84 


108 


90 


120 


66 


72 


78 


84 


90 


* 


96 


* 


66 


72 


78 


84 


90 


* 


96 


* 


66 


70 


70 


70 


90 


* 


96 


* 


66 


72 


78 


84 


90 


* 


96 


* 



** 
** 
** 

* 
* 



Full extension 
Full extension 


** 


** 


** 


** 


Full extension 
Full extension 
Full extension 
Full extension 







Shell to Dead Plate 






42 


42 


42 


42 


78 


96 


84 


102 


36 


38 


40 


42 


78 


96 


84 


102 


** 


** 


** 


** 


84 


102 


90 


108 


** 


** 


** 


** 


84 


102 


90 


108 



Min. diam. of 
furnace 36 in. 



** 



* Combinations not recommended as smokeless settings. 
** Combinations not ordinarily met with in practice. 

t Not adapted to water-tube boilers, 
tt Applied only t j water-tube boilers. No. 8 better for H. R. T. boilers. 

t Exceptionally wide settings will need more head room to take care of extra spring of arch. 



92 



FURNACES AND SETTINGS 



Classification of Settings 

IN the burning of fuels economy is represented by completeness of com- 
bustion and smokelessness. As this depends upon the style of setting, air 
supply and method of feeding coal, it is used by H. Kreisinger as a basis 
for classifying furnaces, as shown in Fig. 19. At (A) is a hand-fired furnace 
into which the coal is fed intermittently on the top of the fire. The air 



Coa/ 



Distillation.^ . «s 
lone \ O 





Hand Fired Furnace 



Distillation ^^^<^ 1 1 U \^^^ 



B 

Side Feed Stoker 




K Distillation 
% f lone 




C 
Chain Grate 



Underfeed Stoker 



Fig. 19. Classification of Furnaces According to Method of 
Feeding Coal and Air. 



comes in a continuous stream through the grate, from the bottom. Some 
air should also be supplied over the fuel-bed. _ 

In the side-feed stoker (B) the coal is fed continuously from the 
side and the air from the bottom at right angles to the path of the coal. 
The coal moves down the grate by gravity and by the agitation of the 
grate bars. Air can also be admitted through special tuyeres placed imme- 
diately above the fuel-bed, at the entrance of the coal into the furnace. 
Some' air enters through the coal in the magazine. 

The diagram (C) shows a furnace equipped with traveling or chain 
grate. The feeding of the coal is accomplished by the motion of the grate. 
The air and coal are both fed continuously, the air being fed at right angles 
to the coal path. Additional air is supplied through the coal in the maga- 
zine, through the thin fuel-bed near the bridge wall, and through leaks along 
the side walls. 

In the underfeed stoker (D) the air and coal are fed uniformly and 
in the same direction. Air is also admitted through the damper in the front 
door of the furnace. 

These styles of furnaces are shown in the following illustrations with 
settings of Heine boilers as installed in modern plants under standard as well 
as special conditions, and for a variety of fuels. In practice each problem 



FURNACES AND SETTINGS 



93 



has to be studied to decide upon the proper furnace design and proportions. 
Generally a change in the location and in the type of tile used in the baffles 
will give furnaces for particular combustion requirements. 

In vertically-baffled boilers the extinguishing action of the tubes, with 
the short flame travel, produces an undesirable amount of smoke. If the 
combustion in these boilers is to be smokeless the furnace volume and there- 
fore the setting height must be increased considerably. Even then the mixing 
effect of the bridge wall and combustion chamber are absent. 

The horizontally-baffled boiler has the necessary furnace volume with 
the ordinary height of setting. Horizontal baft'les, in hand or stoker fired 
boilers, permit a long travel of unchilled flame and maximum time for com- 
pletion of combustion. The turn of the gases at the bridge-wall disrupts 
any tendency to stratify, and this mixing effect also promotes combustion. 



Settings for Hand Firing 

TN burning bituminous coal, it is not practicable, according to O. Monnett. 
^ to combine a hand-fired furnace with a vertically baffled water-tube boiler. 
To prevent smoke the furnace must be arranged with a horizontal baffle, 
as in Fig. 20. In this design the lower part of the tubes over the fire is 
left bare by using T-tiles for the baffle. For the high temperature zone 
over the bridge wall and for some distance back of it, the tubes are entirely 
encased in C-tiles. This part of the baffle is extended from the T-tiles 
to the deflection arch provided to mix the air and gases thoroughly. 








pmmmmmmmmmM^ 



Fig. 20. Hand-fired Setting for Bituminous Coal (Areas of Passages 
are given in Percent of Grate Area.) 




o 
PQ 



CO 

c 

CO 

■M 

CO 

<u 
G 
'v 

X 
o 

c< 

«-t 

C 
'S 

*3 

c 
o 
u 

d 
d 

c 
o 

■4J 

bO 

IS 

CO 

CO 



o 
o 

u 
CO 



ffi 



a; 
U 



FURNACES AND SETTINGS 



95 



The proportions of the furnace for this setting are determined on a 
basis of grate area. The parts are placed so that there will be from 20 to 
25 per cent of the grate surface in the free opening above the bridge-wall, 
40 per cent between the bridge-wall and arch, and 50 per cent free area 
under the arch. The installation of four siphon steam jets, placed across 
the furnace above the fire doors, is recommended to give a secondary air 
supply. This type of setting has been successful where soft coal is used 
and where municipal smoke ordinances are enforced. 

Another form of setting for hand-firing of bituminous coal is the down- 
draft furnace, shown in Fig. 25. Boilers so arranged have given excellent 
results both in smoke prevention and in fuel economy. 

As anthracite coal runs much lower in volatile matter than bituminous 
coal, the flame is much shorter and practically all of the combustion occurs in 
the fuel-bed. The style of setting shown in Fig. 21, can be used for such 
service. The T-tiles are placed on top of the first row of tubes. This 
leaves the bottom of the tubes exposed to the heat of the fire but still forms 
the roof of a combustion chamber in which the gases are retained and 
thoroughly mixed until combustion is complete. 



^^^^^^^ 




Fig. 21. Setting for Hand-firing of Anthracite Coal. 



96 



FURNACES AND SETTINGS 



When the distance between the grate and first tube bank is greater than 
thpr .ho^vP in Fi- 21 the lower baffle can be placed on the second or third 
row of ub s In another modification, Fig. 22, the baffle on the lowest 
row of tube? is not used, and the bridge wall is built up to the bottom row 
of tubes. 




Fig. 22. Alternative Setting for Hand-firing of Anthracite Coal. 



Grates for Hand-Firing 

'THE o-rate in a boiler furnace not only supports the fuel-bed, but also 
1 admks the air for combustion. It is almost invariably made of cast iron, 
which melts at about 21C0 deg., while the lower layer of the fuel-bed on it is 
Tt abouTTwO deg. temperature. A grate does not become very hot when the 
a r is passing through it, and it is further protected agamst high temperatures 
by he insulating effect of the layer of ash between the grate bars and the 
fuel The surfaces and air spaces should be so proportioned that they will be 
kent uniformlv cool by the flowing air. However, with a burning fire on he 
grate and he draft obstructed or shut off, heat will accumulate, and the 



FURNACES AND SETTINGS 



97 



grate will become red hot. If the grate does not burn out or melt and fall 
into the ash-pit at this high temperature, it will be twisted, warped, and will 
sag. The same harmful effects are caused by accumulations of ash and burn- 
ing coal in the ash-pit. 

Cast iron is weak at a dull-red heat and the high temperature causes it 
to grow. Repeated heating will cause a grate bar 15 in. long to grow Yi in., 
according to W . J . Keep, and the pressure it will exert on the dead plate and 
bridge wall will force it into a curved shape, unless proper provision for 
expansion is made. The strength of cast iron decreases rapidly above 680 
deg.. which is about the ordinary temperature of the front grate bar. At 
this temperature the tensile breaking load is 23,750 lb, per sq. in., while at a 
temperature of 1250 deg. the breaking load is only 8,023 lb. per sq. in. After 
being reheated cast iron never contracts to its original length. The cast iron 
for grates should be composed of the highest grade materials having great 
heat-resisting qualities, so that the grate will expand and contract evenly. 

Hand-fired grates are of the stationary, shaking, dumping, and the com- 
bined rocking or shaking and dumping types. Grate bars are manufactured 
in numerous patterns and designs with curved or flat tops. The styles used 
for the burning of the regular sizes of coal are illustrated in Fig. 23. 




Ordinary 



Ag!t;t^t;t;t;t;t^ti;txit;t^t;t;t^t;t;t^t;t»jt^ 




Herringbone 




"tjiiiiiiiiiiiihii,,. npp^ 




Fig. 23. 



Slotted 
Typical Styles of Stationary Grate Bars. 



The style of grate bar and the number, size and shape of air spaces 
are determined by the coal for which the grate is to be used. The free 
area through the grate should not allow the coal to drop through into the 
ashpit, but should be large enough to prevent clogging with ashes and 
cinders. Air space areas of 30 to 50 per cent of the total grate area have 
l)een found satisfactory with natural draft. It is common practice to allow 
% in. air space for No. 3 buckwheat, % in. for No. 2 buckwheat, 5/16 in. for 
No. 1 buckwheat, ^4, in. air space for pea coal and J/2 in. openings for bitu- 
minous coal. 

In small plants, where larger sizes of anthracite are burnt, the plain 
grate is probably as satisfactory as any ; when coals of high ash content and 
which clinker are used, the shaking or rocking grate is to be preferred. The 
grate must be so constructed that the moving parts will not clog and so 
that their action will break up the clinker. 

Anthracite dust, silt, culm and screenings are burnt on grates with small 
openings and require mechanical draft. 



FURNACES AND SETTINGS 



99 



Hollow grate bars, with a blower system, are sometimes used for burn- 
ino- sawdust, chips, shavings, tanbark and bagasse. Such grates should 
ha%e large air spaces so that partial filling-up of the openmgs will not niter- 
fere with the air supply for proper combustion. In making up the required 
grate surface, the hollow bars are sometimes alternated with ordmary bars 
to suit the fuel. 




Fig. 24. Water Grate. 

Grate bars are generally made in sections not more than 3 ft. long, so 
that the total grate extension is a multiple of this length. Grate bars are 
3 to 6 in. deep at the middle, tapering down to about 1 in. at the ends. To 
allow for expansion, the bars are usually made about 2 per cent shorter 
than the space for which they are intended, so that they will f^t when the 
boiler is operating. Most grate bars are in one piece, although some have 
a body portion and a removable sectional top, which contains the air spaces. 

The total grate length is limited by the physical ability of the fireman to 
throw the coal to the farthest end. Grates 10 to 12 ft. in length are some- 
times used for anthracite. The limits for bituminous coal are 6 to 8 ft. 




Fig. 25. Water Grate as Used in Down-draft Boiler Setting. 



100 



F I' R X A C E S AND S E T T T X G S 



because it is more difficult to handle the fire. Long grates are usually 
inclined from -74 in. to V^ in. per foot in length toward the rear, so as to 
aid in hring. 

Down-draft settings for the smokeless combustion of soft coal utilize a 
so-called n-atcr- grate. Fig. 24, which is placed above the ordinary grate in the 
boiler, as shown in Fig. 25. The water-grate consists of a series of pipes 
fastened to steel headers, so connected to the boiler that water will circulate 
through it. Fresh coal is fed onto the water grate, and the air admitted 
above it travels downward through the fuel-bed. As the coal becomes partly 
consumed, it falls through to the grate below% where the combustion is com- 
pleted. The space between these two grates is the combustion chamber, in 
which the gases are consumed before passing through to the chimney. 

Settings for Mechanical Stokers 

WITH chain grate stokers, Heine boiler settings are as shown in Fig. 26. 
The t'les of the lower baffle are placed on the first row of tubes, either 
encircling the tubes entirely or exposing the bottom half. A head room 
of 7^4 feet fromx the floor line to the underside of the waterleg gives the 
desired furnace proportions. This dimension may vary considerably without 
affecting the boiler performance, but should not be less than 6Y2 feet. This 
setting has been found to give good economy and smokeless operation for 
loads uo to 200 per cent of rating. 




0't(f/ff//y/ j//^^//^////J//////>/////M 



•■/<>-■' 



Fig. 26. Chain Grate Setting. 

With side-feed or double inclined stokers, the boiler can be set with an 
extended furnace or with a flush front. In the t>pical setting. Fig. 27, 
the bottom row of tubes is enclosed in baffle tiles to give a solid roof, and an 
auxiliary bridge wall breaks up the currents of gases and insures a thorough 
mixture. The side-feed stoker combined with a vertically baffled boiler will 
not gne smokeless combustion. With horizontal baffles a 7'_>-ft. clearance 
is sutticient between the bottom of the front header and the floor line. 



1-^ U R N A C F. S A N l^) S K T T T X G S 



101 



The 07:cr-fccd type of stoker fits in at the front of the boiler and has 
a shaking or dumping grate at the foot of the bridge- wall. For boilers with 
horizontal baffles, a 6-ft. setting is required, while for vertical baffles the 
clearance should be aliout 9 feet. Fig. 28 shows a Heine boiler and a front- 



%W/MW///////////y 





*v >> VY S\^^ s^S^^?^ -N^ yy ^^^s^^ys-s^s>^>^'-^vs-y^V v.^T^ 



VM 



Fig. 27. Side Feed Stoker and Extension Furnace Setting. 



feed stoker. Tlie typical l)affle arrangement is used, but deflection arches 
or piers sometimes aid in mixing the gases. When the clear opening between 
the top of the bridge-wall and the bottom of the hrst row of tubes is not 
less than 40 per cent of the grate area, piers are not required. 









c 




"S 


u 




'0 


o 


PQ 


o 






•0 


4-J 


Wi 


d 


ns 


CS 


•0 


E 






4-1 


CO 


W 


15 




H 










■53 


6 


ffi 


U 


14-1 







N 




•S 


P4' 


'C 




w 


K 


•-^ 



10 


• 


(M 


w 


o> 




W 


(U 


u 


A 


;^ 


+J 


2 


o 


!§ 




■« 


■M 


J2 


G 


;3 


cc 


C/3 


S 


ta 




-M 


rt 


.« 


Oh 


fi 




"< 


^ 


•d 


bD 


<u 


u 




13 


"cO 


XI 


•M 


w 


OT 


■M 


c 


■M 


HH 


cC 


M 




CO 


(U 


j: 


X! 




■4-1 


>» 


c 


CO 


• »H 


a 


CO 


a 


(U 







U 


■5 




m 




T3H 


u 




cS 








OS 


(U 


■*-> 


^^ 


Xfl 


■5 


0) 


PQ 


.s 


'O 




u 
CO 
•0 




C 


Oh* 


cC 

■M 


• 


CO 


K 


(U 


t^ 


.S 





'C 


VO 


ffi 





(4-> 


^ 





H 


Ph' 


W) 


, 


.S 1 


K 


•M 










lU 





Ih 


in 


u 


10 



FURNACES A X D SETTINGS 



103 




Fig. 28. Setting for Overfeed Stoker. 

With the nnderfccd stoker, the rates of combustion are usually high, 
so that a great volume of combustible gas has to be burned in the 
furnace before being chilled by the boiler surface. For this reason, the 
standard Heine furnace design, Fig. 29, is generally retained. The settings 
can be lower for the horizontal types of underfeed stokers than for the in- 
clined types. 




Fig. 29. Setting for Horizontal Underfeed Stoker. 



104 



FURNACES AND SETTINGS 



Fig. 30 shows a Heine boiler and superheater set for mechanical draft, 
and an underfeed stoker of the inclined type. The headroom between the 
waterles- and the floor line is about 7 feet. The lower baffle is made to 




mm 



Fig. 30. Inclined Underfeed Stoker in Heine Boiler, Equipped with 
Superheater and Mechanical Draft. 



enclose the tubes. By changing the tile to the third row of tubes, the setting in 
Fig. 31 is obtained. In this, more heat is absorbed by direct radiation, and 
excessive furnace temperatures are avoided. 



F U R N A C E S A N D- S E T T I X G S 



105 



By installing double stokers, boiler capacity and efficiency can he in- 
creased for almost the same space. One stoker is placed at the front and 
one at the rear of the setting-, as in Fig. 32. By forcing a greater weight of 
--•ases through the boiler, the capacity is increased. The larger furnace 




Fig. 31, Modified Stoker Setting. 



volume gives better combustion ; also, a larger proportion ot heat V; » ^^l'; ^d 
to the boiler. At heavv loads the overall efficiency is highci than when 
one stoker is used. Anv variation in the efficiency is due to changes in the 
furnace operation, because the efficiency of the boiler, proper, as a heat 
absorber, is practically constant. 



106 



FURNACES AND SETTINGS 



Methods of handling coal and ash are discussed in Chapter 16 on 
OPERATION. 




Fig. 32. Double Stoker Setting for Heine Boiler with Superheater. 



FURNACES AND S K T T T N (-. S 



107 



Ashpits 

THE ashpit is made of concrete or brick. The design depends upon the 
boiler load, kind of coal, type of furnace, whether hand or stoker fired, 
and of setting. Ashpits satisfactory with a mechanical or pneumatic system 
may give trouble for hand removal, while pits for hand operation may also 
prove satisfactory with a conveyor. 

The ashpit should be large enough to accommodate the ashes from an 
18 to 20-hr. run. Such pits elimmate the handling of ashes by the night shift. 
They also protect the grates or stokers against destruction by the action of 
accumulated ash and clinker. In practice, however, ashpits for hand-fired 
furnaces are seldom of more than an 8 or 10-hr. capacity. Pits having capac- 
ities of 12 to 14 hr. are generally provided for stoker installations. 

To proportion the pit for a given period, the maximum amount of 
fuel that can be burned on the grates must first be determined. The maximum 
percentage of ash or refuse should be figured on the basis of the lowest 
grade of fuel to be burned. The pounds of ash and refuse to be handled 
per hour is the product obtained by multiplying the percentage refuse and 
the hourly fuel consumption. The volume is determined by allowing 40 lb. 
of ash to the cubic foot. The total capacity required then depends upon the 
periods of ash removal. 

Ashpits should be so accessible that they can be easily cleaned ; otherwise 
the work may not be attended to regularly, and the grates or stoker mech- 
anism v/ill be damaged. Fairly small pits are easily cleaned and give better 
results than large pits, which involve heavy labor. Ample room must be 
provided for the use of a hoe or shovel. The pit should be not longer than 
8 feet. Doors, gates or valves, as used on hoppers, should be arranged to 
open and close easily and should be accessible from the floor. Means of 
inspection should be provided to make sure that all the ash has been dis- 
charged. With reasonable care, the cost of ashpit repairs or relining can 
be kept low. 

Some typical designs of ashpits are given for different operating con- 
ditions. The simplest form is the usual pit for hand-fired furnaces, as shown 
in Fig. 33. 




■J.TI- ft A-": 



Fig. 33. Common Ashpit for Hand Firing. 



A modification to obtain greater ash capacity without sacrificing ease of 
ash removal is shown in Fig. 34. 




Grand Central Terminal of the New York Central Railroad, New York City 
in course of construction. This building contains 8550 H P ^' 

of Heine Standard Boilers. 



F IT R N A C E S AND S R T T I N G S 



109 




Fig, 34. Large Capacity Ashpit for Hand Firing. 



A common form, particularly for side-feed stokers, is shown in Fig. 35. 
The cost of construction and maintenance is low ; Imt it is very difficult to 
remove ash from pits of this form unless a pneumatic or steam conveyor 
is used. 




Fig. 3 5. Rectangular Ashpit of Large Capacity. 



In modern stoker-fired plants it is the general practice to use hopper 
ashpits. The labor of handling the ash is greatly reduced and the installa- 
tion of ash conveyors is more convenient. The tunnel under the firing floor 
enables the ash to be easily hoed from the hopper ashpit into conveyors 
or ash cars without interfering with tbe work on the firing floor. Fig. 36 
shows an example of such an arrangement. 



110 



FURNACES AXD SETTINGS 



This system is also frequently used in hand-fired furnaces burning very 
low grade fuels having a high ash content. Dumping grates or dumpmg dead 
plates are then generally used. 




O 



ii 



\^.^itt 



x^ 









m 







-M 



1 

















# 



Wi^^■^yo-.■■.'?^-^^ 

■*£3-.i<i:V.«.'»: ■; 



Fig. 36. Hopper Ashpit and Tunnel. 



\ still more convenient method which is adopted m most modern power 
plants is to provide a basem.ent as large as the boiler room Ample space 
is then available for ash-handling apparatus, forced-dralt air ducts and other 
auxiliaries : and the removal of ash is done under more comfortable condi- 
tions. A tvpical arrangement of this kind is shown in Fig. 37. 



F U R N A C K S AND S E T T [ X G S 



111 




Fig. 3 7. Hopper Ashpits with Basement under Boiler Room. 

In man}' cases separate hoppers are provided to receive ash and clinker, 
and to recover coal dropping from the front part of the grate. The com- 
bustion chamber is often provided with a hopper bottom to facilitate the 
removal of dust. 

Some suggestion on the design of ashpits may also be obtained from 
chapter on mechanical stokers, and from the part of the chapter on economi- 
cal boiler operation, referring to ash handling. 

Hopper ashpits should be lined with firebrick. There is always the 
possibility of combustible matter burning in the ashpit owing to careless 
operation of mechanical stokers or dumping grates, and fairly high tempera- 
tures are often encountered in such cases. 

Ash doors and valves at the bottom of hopper ash-pits should be air- 
tight or nearly so. With natural draft sufficient air will be drawn in through 
leaky doors to cause brisk combustion under conditions described above, 
and the ash may be melted into large clinkers, which are difficult to remove 
and which sometimes must be broken up before they can be got through 
the doors or valves. With forced draft under pressure in the hopper ash- 
pit, leaky doors may increase the load on the fans and cause wasteful power 
consumption. 

Settings for Powdered Coal 

TDOWDERED coal has been used extensively for the past twenty-five 
-*- years in certain metallurgical processes, particularly in the cement indus- 
try, and its success in this and similar industries is amply testified by its 
extensive use. Certain characteristics in the combustion of pulverized coal 



112 



F U R X A C E S AND SETTINGS 



have brought out the fact that under some conditions it is feasible to 
utilize this fuel for use in generating steam. In the past five years a number 
of boiler plants have been equipped to burn this tj-pe of fuel. 

Boiler furnace setting design for the successful combustion of pulverized 
coal was a subject which was not thoroughly understood when the first 
installations of this sort were made, and hence the early results obtained 
were not satisfactory'. However, the subject is now past an experimental 
stage and it can be said that the following remarks on furnace design are 
in general indicative of good practice. The furnace volume should be so 
proportioned that combustion is completed before the tube bank is reached. 

About 2 to 2y2 cu. ft. of furnace volume should be provided for each 
boiler horsepower developed, assuming that the combustion chamber is nearly 
in the form of a cube. Boiler furnaces are not always of cubical form, so 
that the velocity of the gases should be limited to 7 ft, per second, through 
the smallest cross sectional area and where the temperatures are highest. 
This rule for contents holds good for coals in which at least 25 per cent of 
the total combustible is volatile matter. It does not apply to anthracite, 
coke breeze, or other low volatile fuels. 

An extension furnace is usually employed to obtain the required com- 
bustion space. Inasmuch as the ash will tend to adhere in the form of slag 
on furnace sides and bottoms, it is desirable to have these surfaces slope 
downward to a slag hole, through which the molten slag can be tapped off. 
Furnace temperatures are high in this class of firing, and it is essential that 
the walls be heavy and constructed of first quality refractories. 

Fig. 38 shows a Heine cross drum boiler with a typical setting for burn- 
ing pulverized coal v.'ith the Bonnot system. 




Fig. 38. Typical Powdered Coal Setting. 



FURNACES AND SETTINGS 



113 



The use of powdered coal necessitates the installation of a pi-e])aiation 
plant, which generally consists of a crusher, a dryer, a pulverizer and suit- 
able elevators, conveyors, dust collectors, hoppers, etc. Fig. 39 shows the 
layout of a typical preparation plant. 




c 

13 
o 

O 

T3 
(U 

o; 
o 

u 

a 

u 

CO 
CO 

u 
u 
u 



a 

B 
a 



s 



CO 



114 




<4-> 

a 
CO 



4) 



V 

o 

CO 



CO 



o 

VO 



u 
CO 
0. 



FURNACES AND SETTINGS 



115 



Powdered coal requires care in handling. In a well-designed and prop- 
erly operated plant there is but little danger from explosions, iriowever, 
where hoppers, conveyors, elevators and dust collectors are not tight, and 
the powdered coal is allowed to escape into the room, there is great liability 
of explosion due to the possibility of the ignition of the cloud of coal dust 
by an open flame. 

Pulverized coal when newly ground is practically a fluid, because of the 
entrained air, hence it is readily handled by conveyors and flows easily from 
hoppers. But, after standing from 36 to 48 hours, the entrained air escapes 
and the coal settles down and packs in the hoppers. The correct way to 
overcome the difficulty of packed hoppers is to provide compressed air lines 
in the hopper sides and thus agitate the packed coal with air, supplemented 
by hand poking. Hammering the hopper sides to make the coal flow only 
causes it to pack the tighter in the bin. The sides of powdered coal hoppers 
should have a slope of not less than sixty degrees. 

In order to handle the crushed coal in the pulverizers it is generally 
necessary to dry it down to fiom one to two per cent moisture content. 
The pulverizer is generally adjusted for grinding the coal down to a fineness 
of 85 per cent through the 200-mesh sieve, and 95 per cent through the 100- 
mesh sieve. The better combustion conditions obtained with coal of greater 
fineness than given above does not warrant the cost of the extra pulveriza- 
tion. 

Powdered Coal Burners 

II} URNER Installations usually include a feeder of the screw conveyor 
-*-^ type, such as Fig. 40. The capacity of the feeder depends upon the pitch 
and depth of the screw, while the amount of feed is controlled by its speed, 
which is adjusted by a variable speed motor drive. Air for feeding and 
mixing is supplied by a blov/er at 6 oz. pressure. The fuel, as it drops into 
this blast of air, is agitated by a paddle wheel so that the mixture of air 




Fig. 40. Lopulco Type Variable-speed Fuel Feeder. 



116 



FURNACES AND SETTINGS 



and coal remains practically of constant density nntil injected into the fur- 
nace. The type of burner recommended with this equipment is shown in 
Eior. 41. 




Fuel ariK 
Air Inlet 



Damper 
Fig. 41. Lopulco Type Pulverized Fuel Burner. 



In the burner shown in Fig. 42. a variable speed screw feeder at the 
bottom of the pulverized fuel bin delivers the coal, the amount being regu- 
lated by a hand wheel. A feeder of this type having a capacity of 500 lb. 
of fuel an hour can be regulated to deliver as little as 26 lb. an hour. There 
are tv/o air supplies, botli controlled by blast ga^es. The air for combustion 
is at 1^-oz. pressure, while the air conveying the fuel is at 6-oz. pressure, 
expanding down to ly4-oz. in the burner. The burner used is of cast iron 
pipe with a specially shaped elbow in which the fuel pipe is placed. 



Primary Air 
Q.oz 



Powdered 

" Fuel Bin 





Secondary Air 
l^oz- 



Blast Gate- 




Feeder 



-—^Jnand \ C 



'" Blast Gate 




Peep Hole- 



Furnace 
Wall -- 



^ 



Burner- 
Fig. 42. Quigley Burner Arrangement for Powdered Coal. 




In another Inirner arrangement no mechanism whatever is used. The 
air in motion through a mass c>\ powdered fuel picks up sufficient fuel to 
make a combustible mixture. 

According to W . A. Ezaiis, the control of the fuel supply to the burners 
l)y air regulation rather than by varying the speed of a screw feed gives best 
results. The speed of the screw conveyor cannot be adjusted closely, but the 
air blast is subject to exact control. For any given feed adjustment, a 
burner arrangement should deliver the required fuel with not more than a 
3 per cent variation in quantity for any number of 5-min. intervals. 



F U R N A C 1^. S AND SETTINGS 



117 



Settings for Oil Burning 

THE ii?e of petroleum as fuel for steam generation has increased remark- 
ably within the last decade. This has been brought about by the abun- 
dant supply resulting from the development of new oil fields, and by certain 
advantages of oil tiring over coal firing. But as the supply of petroleum 
suitable for fuel has not kept pace with the unusual demand, uncertain 
deliveries and increasing cost are now working to the disadvantage of those 
plants using oil. There is no doubt but that oil ranks second in importance 
to coal as fuel for steam generation, but with the present rapid depletion of 
oil resources it is evident that oil firing will never supercede the use of coal. 

In general the petroleum used for steam generation is of two types, the 
one commonly called fuel oil is the heavy oil resulting from a partial refin- 
ing of paraffin crude, and the other is the unrefined, asphaltum-base, crude 
oil. The oils found in the mid-continent and Eastern fields contain a paraf- 
fin base, while those produced in the Gulf and Western fields contain an 
asphaltum base. A discussion of petroleum with typical analysis is given in 
Chapter 13 on FUEL. 

The success of oil firing depends largely upon proper furnace design, 
and there are a number of important points which must be considered. 
First, a large amount of refractory radiating surface must be provided to 
assist in combustion. Good practice in this regard is to allow from 0.9 to 1.2 
square feet of radiating surface per boiler horsepower developed. Second, 
the furnace volume must he so proportioned that the gases are given time 
for complete combustion before reaching the comparatively cool heating 
surface. A combustion space of about 2.0 cubic feet per developed boiler 
horsepower will satisfactorily meet the average volumetric requirements. 




Fig. 43. Typical Oil Burning Setting. 



FURNACES AND SETTINGS 119 



In proportioning both radiating surface and combustion space, the proposed 
ratings at which the boilers are to be operated should be used in the calcu- 
lations rather than the manufacturers' nominal rated horsepower. 

The setting of the Heine boiler, with its large combustion space and 
ample refractory radiating surface, satisfactorily meets the requirements of 
oil firing. A typical setting is illustrated in Fig. 43. 

The location of the burners in oil-fired setting design, should be such 
that the flame action will not be localized on portions of the heating surface, 
so that trouble from blow-torch action with the resultant blistering of tubes 
will be obviated. The oil or flame should not impinge directly on any por- 
tion of the furnace brickwork, because when starting up a furnace the oil 
dripping down after impingement on such cold surfaces may collect on the 
floor of the combustion chamber in such quantities that a serious explosion 
may occur when this pool of oil becomes heated up to the ignition point. 

Certain features in chimney design for oil firing are discussed in 
Chapter 6 on CHIMNEYS. 

Oil Burners 

ONE advantage in the use of oil for fuel lies largely in the fact that it 
can be broken up into minute drops so that the air for combustion comes 
into intimate contact with every particle of the liquid with the combustible 
gases evolved. The requirements for efficient combustion are a chamber of 
the proper proportions with the correct air supply properly distributed, and 
the thorough atomization of the entering fuel, the term "burner" being applied 
to the atomizing device. The desired effect is secured either by the action 
of steam or compressed air, which atomizes the oil and carries it into the 
furnace, or by purely mechanical means. 

There are many types of oil burners and these are arranged differently 
because of tlie method of operation and the shape of the flame. Sometimes 
the oil is sprayed out in a fan-like flame between firebrick blocks, which form 
the approximate boundaries for the flame. 

The burner can be inserted through the firing door, with the grates cov- 
ered with checkerwork with ^-in. space between the bricks, but the "low 
setting" is preferred, in which the grates are removed, and the checkerwork 
laid on supporting brick in the ashpit and the bridge wall cut level with the 
top of the checkerwork. 

Steam atomizers include outside mixers, in which the steam impinges on 
the oil current just beyond the tip of the burner, and inside mixers in which 
the two come into contact within the burner. A combustible mixture of atom- 
ized liquid and volatile gases issues from the nozzle. In air atomizers, a jet 
of air under high or low pressure is used to break up the oil, part of the 
air for combustion entering in this manner. With mechanical atomizers the 
oil, preferably heated, is forced out under pressure through a distributing- 
tip, or by the whirling action of a revolving carrier. 

Burners utilizing steam for atomization are installed in many stationary 
oil-burning power plants. They produce thorough atomization, with a long- 
flame, but cannot be used where the steam would be liable to condensation, 
and great care must always be taken to keep the steam consumption down 
to a minimum. Air atomizers are desirable in marine work or in stationary 
plants where it is necessary to conserve the water supply, and they have the 
further advantage that the latent heat in the exhaust from the blowers or 
compressors is returned to the boiler, and no heat is carried away by the 
steam in the flue gases. They give a short, intense flame and the furnace brick- 
work must be proportioned accordingly. Under proper conditions, either 
steam or air atomizers can be operated with a stean-i consumption of 2 or 
3 per cent of that produced by the boilers. Mechanical atomizers require 



120 



F U R X A C E S AND SETTINGS 



little .-team, and their exhaust can all be returned to the boilers. Tnej- are. 
in general, susceptible of ven.' nne adjustment to meet var\-ing load con- 
ditions. 

Illustrated below are several t>~pes of burners now on the market. 

In the Hammcl Burner, Fig. 44, the oil, either heated or cold, is fed into 
the upper pipe, is forced through the sloping passage in the burner to the mix- 
ing chamber C. Here it encounters the entering steam jet at an angle, the 
hea\->- hydrocarbons are atomized, and the lighter ones vaporized, and the 
mixture issues from the burner to the combustion chamber. Thin renewable 
plates forming the top and bottom of combustion chamber C receive any 
wear due to grit in the oil. while moisture carried in with the steam flows 
along the lower passage and is blown out under the steel plate. The Ham- 
mcl Oil Burning System is ordinarily installed without arches, bridge walls 
or target walls. 







a 




u u 



er -ead. 



Head 






Sfea' 



Fig. 44. The Hammel Oil Burner. 



T3 — ZT 



The Staf'lcs & Pjcifcr Burner, Fig. 45. operates with steam or air, 
which flows through the large pipe encasing the oil pipe, until it enters the 
mixer, which is set with the apex P slightly below the center of the tip. 
The flow of oil is regulated bj* the valve rod inside the steam pipe, operated 
bv the wheel shown. 




/?./ 



Fig. 45. The Staples and Pfeifer Oil Burner. 



1-^ I' R X A C J-: S A X USE T T 1 X G S 



121 



Tn the focrst Fuel Oil Burner, Fig. 46, the oil under gravity or pres- 
sure feed flows in through the lower pipe, and the atomizing steam or air 
through the upper pipe. The illustration shows a fan-tail burner, although 
burners giving a cone-shaped flame are also furnished. 




Fig. 46. The Foerst Fan-tail Type Oil Burner. 



The ir X. Best Calorcx Burner. Fig. 47. is an cxiernal mixer, employ- 
ing a jet of the atomizing fluid issuing at right angles to the oil. Ihe atomizer 
lip is held tightlv, but can be raised for blowing out incrustations with the 
aid of the by-pass. Burners are made for throwing a long, narrow flame, or 
a fan-shaped one up to 9 feet wide. 




3 



Oh 



CO 

> 

V 



a 

u 



o 
O 



1) 

a 
a 

"3 



o 



CO 
CO 

V 

G 



FURNACES AND SETTINGS 



123 



By- Pass 
Valve- 




^Orj 



Fig. 47. The W. N. Best "Calorex" Oil Burner. 

The Koerting Cyclone Oil Burner, Fig. 48, is designed for use where 
forced draft is required, or where it is desired to make use of a low pressure 
oil pump already installed. The oil issues from an atomizing nozzle, while 
the pipe through which it flows is surrounded by a passage carrying com- 
pressed air, which receives a gyratory motion, so that the mixture coming out 
of the cylinder forms a spreading cone, in which the flame remains close to 
the burner. Air atomizing burners are also supplied, and burners for use 
where the oil is under gravity, as in small plants. 




Ji'r Blast 
Connection 



Air 
Recjisfer 



Fireclay 
Cylinder 



Fig. 48. The Koerting Cyclone Oil Burner. 



Of more general application is the Koerting Mechanical Oil Burning Sys- 
tern, in which the fuel is pumped at high pressure to centrifugal spray nozzles, 
at a temperature of about 260 deg. F. The burner is surrounded by an ad- 
justable cylindrical air register, admitting air through rectangular openings, 
giving an intimate mixture of combustible material. 

The Cocn System, Fig. 49, utilizes a mechanical burner into which the 
oil is pumped under pressure and receives a whirling motion. The adjusting 
wheel shown in the sketch is used to regulate the flow; by turning it the small 
ball at the cone end can be lowered, reducing the flow to a minimum without 
shutting it of¥. 



' OS 



FURXACES AXD SETTINGS 



Adfush'nq 
Wheel 





Shui-off 
Valve 



Y\a. 49. The Coen Oil Burner. 



The /?av Roiarx Burner, Fig. 50, atomizes the oil m an open cup. re- 
volving at hiVhspLd, while a^r under V. lb. pressure issues from a cylmdrical 
slot surrourdki-^e atomizer and directs the mixture into the furnace. The 
;umpblo^^r and atomizer are driven by a 34 H. P. motor, and can be swung 
from the furnace front. 




Fig. 50. The Ray Rotarj^ Crude Oil Burner. 
Oil a^ fuel requires the use of certain auxiliarj- apparatus, most Important 
" t^'sf m^s^L^rTc^lin^ior oU pump and condensing ^e hea1.r 

set manufactured by the G. E. Witt Co. The oil, -^^^Xourh^^Vtraifer t^^ 
numo is delivered to the heater, after which it passes through a strainer to 
?he oil burner line The heater consists of copper tubes, through which 
the exhauTsteam from the pump circulates, heating the oil m the cast iron 
chamber surrounding the copper coiU. 



FURNACES AND SETTINGS 



125 



Oiu Inlet 

^-■ 

To Pump 




Oil iNLEj^^jTlll 



To Heater 



0il5trainer 

/ 



.Outlet 
To Burners 



5ectionThru 
Heater 



Fig. 51. Witt Oil Pumping Set with Condensing Type Heater. 



Tar Burning 

"VV/ATER gas tar, which is a by-product from gas works using the water 
^^ gas system, makes excellent fuel for use under steam boilers. An aver- 
age tar will have a calorific value of about 15,000 to 17,000 B. t, u. per 11). 
and will weigh about 9.5 lbs. per gallon. 

In general it may be said that a furnace suitable for burning crude oil 
will give satisfactory results when using water gas tar as fusl. Refer to 
remarks given elsewhere on oil burning furnace design. 

Crude oil burners can be satisfactorily used for burning tar, though 
provision should be made for straining the tar before it reaches the burner, 
and clean-out connections for blowing out tar lines and burners with steam 
or compressed air should be provided. Inasmuch as a low flash point is a 
characteristic of water gas tar, it should not be preheated beyond the tempera- 
ture at which it is sufficiently fluid to be handled. 

Coal gas tar may be used for boiler firing, but the present high value 
of coal tar derivatives, which are used as bases for dyes, explosives, etc., 
precludes its use as a fuel. 







CO 

Q 

bB 



PQ 

CO 

CO 

G 
O 

CO 

bO 
CO 

V 
X 

CO 

o 

g 



G 
u 

PQ 

CO 

O 



a 
a 

*3 



o 
PQ 

V 

C 



CO 

c 

CO 

w 

o 



FURNACES AND SETTINGS 



127 



Gas Burning 

NATURAL gas, blast furnace gas, coke oven gas and producer gas are 
the four principal types of gaseous fuels which are available for use 
under steam boilers. 

NATURAL GAS : Natural gas is probably the most widely used of the 
four principle gases, although the depletion of the natural gas fields is now so 
rapid, that its utilization is being rapidly curtailed. 

Representative analyses of natural gas from various locations are given 
in Chapter 13 on FUEL. 

The design of a boiler furnace for burning natural gas involves several 
important points. First, the furnace volume or combustion space must be 
proportioned so that the gases will not come into contact with the cool 
heat absorbing surface until combustion is completed. A furnace volume of 
about 2 cu. ft. per rated horsepower will give sufficient combustion space 
to meet the above conditions. The standard Heine boiler, with its arrange- 
ment of horizontal baffling on the lower row of tubes, gives a furnace 
volume particularlv well adapted for the burning of natural gas. Dutch 
oven furnace construction is not necessary with Heine boilers burning natural 
gas. Second, in order to prevent laning action of the gases in their passage 
through the boiler it is more desirable to use a large number of small 
burners than a few large ones. One burner for 25 to 30 rated boiler 
horsepower will give satisfactory results. Third, where furnace widths are 
over 5'0" it is desirable to install checkerwork to act as an igniter for the 
gases. In some cases one checkerwall placed about three or four feet from 
the burner outlets is used as an igniter and a second checkerwall, sorne 
three or four feet behind the first, acts to break up the flame and mix the 
gases thoroughly after passing through the first. 

Fig. 52 shows a typical natural gas burning setting for a Heme boiler. 



ro fe, 










^(^(';^^.^c^.^/.^:tf.d^-d<-:^\-^d<x:^(d/ rt'^^^ 



^=^:»?:^^ 



Fig. 52. Typical Natural Gas Burning Setting. 



128 



F U R X A C E S A X D S Z T T i X G S 



71: e "Kirkwood" natural gas burner. Fig. 53. consists of an outer and 
inner casing, and a nozzle. Into the inner casing is driven a large number 
of small brass spuds which are drilled half way through in two directions. 
These two holes meeting make a passage for the gas from the annular 
space between the outer and inner casing into the inner cylindrical space. 
Here the gas is introduced in a great number of fine jets into the air which 
is drawn through the burner. Air regulation is obtained by adjustifig the 
front slide. 




End View of Kirkwood Natural Gas Burner. 



Due to die fact that the supply of rjaturai gas in certain localities is 
erratic and uncertain, it is generally the custom to install the burners above 
coal fired grates or even stokers. The grates or stokers are normally com- 
pletely covered with firebrick, but in case of the gas supply failing, the 
bricks can be easily removed, the burner swung out of position and a coal 
fire quickly staned. 

BLAST FURXACE GAS or the gas resulting from the chemical react'on 
in the iron blast furnace, is extensively used for steam generation in the 
iron industrv". 

A t\T)ical analvsis of blast furnace gas is given in the table in Chapter 
13 on FUEL. 

It is to be noted that this gas is "lean" or low in calorific power, and 
that the chief combustible constituent is carbon monoxide. These two facts 
establish the necessity of special furnace design for burning it. The furnace 
volume required will varj- with the quality of gas available and also with 
the type of burner used. With an inside mixing burner, where the air 
necessarj' for combustion is partially mixed with the combustible within the 
burner shell, the furnace volume need not be as large as when the air neces- 
sary- for combustion is induced around the burner nozzle. For average condi- 
tions the furnace volume should be between 2 and 2^2 cubic feet per rated 
boiler horsepower. With this tj-pe of fuel as well as with oil or natural gas, 
the Heine boiler with its large combustion space is particularly well adapted 
for eflticient and high capacity- operation. 



FURNACES AND SETTINGS 



129 



Inasmuch as blast furnace gas contains such a high percentage of carbon 
monoxide, it is necessary to maintain an auxiliary fuel bed to act as an 
igniter. Coal fired grates are most commonly used, but stokers or even oil 
burners are entirely practicable for this purpose. 

It is preferable to use washed blast furnace gas for firing boilers, but 
not absolutely necessary. Where coal fired auxiliary grates are used, the 
dust precipitated in the furnace from the unwashed gas may be removed 
when the fires are cleaned. However, this dust when allowed to accumulate 
becomes fused and is difficult to remove. 




Fig. 54. Kirkwood Natural Gas Burners under Heine Boilers at 
Chartiers Water Company's Plant, Pittsburgh, Pa. 



Due to the fact that pulsations and mild explosions are liable to occur 
when burning this type of fuel, it is necessary that the settings be particularly 
well buckstayed. Quick opening, unlatched explosion doors should also be 
provided in the setting. 



130 



FURNACES A X D SETTINGS 



Fig. 55 illustrates a Birkholz-Terbeck burner, which is ofien applied to 
blast furnace gas-iired boilers. In this burner the primary- air supply is 
admitted through openings in the back of the air nozzle, being aspirated by 
the force of the gas blowing through the burner. The primar}- air supply 
is not sufficient for proper combustion and a secondary- supph* is drawn in 
b}- the furnace draft through the secondarj' openings around the nose of the 
burner. 




Secondary Air '^ 




Fig. 55. The Bixkholz-Terbeck Burner for Blast Furnace Gas. 



Fig. z^ shows a Kling-Weidlein Burner in which the gas leaves the 
primary nozzle at high speed and in two streams, drawing primary- air in 
between the gas streams. The air mixes with the inside layers of the gas 
streams on their way to the ignition chamber, but before the latter is 
reached, the secondary- air in two streams is brought in and mixes with 
the outside lavers of the gas. 



FURNACES AND SETTINGS 



131 




Rzgulafinq 
■ Slide 



Fig. 56. The Kling-Weidlein Blast Furnace Gas Burner. 

In the Bradshaw-Fraser Burner, Fig. 57, the aspirating action of the 
blast furnace gas which has attained high velocity as a result of the con- 
stricted passage is used to draw in air through an internal connection. 




Fig. 57. The Bradshaw-Fraser Gas Burner. 



PRODUCER GAS has but a limited use under boilers, and for the 
sake of economy it should be used only in an emergency. A representative 
producer gas analysis is given in Chapter 13 on FUEL, and it will be noted 
that in calorific power and in percentage of combustible it resembles blast 
furnace gas. 

COKE OVEN GAS is a product of the destructive distillation of coal 
as carried out in the by-product coke oven. This gas has a relatively high 
calorific value, as is indicated by the analysis given in Chapter 13 on FUEL. 
In general, the proper methods of burning this fuel are the same as for 
natural gas. However, as this gas may contain tar, which has not been 
entirely removed in the scrubbing process, it is necessary to have the gas 
lines and burner pipes arranged for easy cleaning. 




C/3 



3 
O 



v: 



'Ji 



CQ 



c 
s 

xn 

u 

"o 

o 

o 
o 
o 



FURNACES AND SETTINGS 



133 



Settings for Burning Refuse 

WOOD chips, shavings, sawdust, and other refuse from sawmills or 
industrial processes require a boiler furnace in which a large mass of fire- 
brick is continuously radiating heat to the fuel and evaporating the moisture 
from it. 

In the Heine boiler, a semi-extension or Dutch oven, Fig. 58, meets 
the requirements of wood refuse or tan bark. The thickness of the fuel-bed 
carried on the grate depends upon the size and nature of the fuel, as well as 
upon the quantity of air that the available draft can draw through the bed. 
A long flame is produced by the burning fuel, but it is prevented from coming 
in contact with the tubes of the boiler by the baffle tiles lying horizontally 
on the bottom row. As wood refuse generally contains a large amount of 
moisture, a considerable percentage of the total heat is consumed in evapo- 
rating the water from the fuel. 




^m^^ ssssss^iw^Mmiimm^Aww^^^^^^^^ 



Fig. 58. Setting with Semi-Extension Furnace for 
Burning Wood Refuse or Tan Bark. 



Fig. 59 shows a method of firing when the wood-refuse is brought to 
the boilers by pneum.atic conveyors, the fuel being deposited in the cyclone 
separator and fed to the boilers through 10 or 12 inch galvanized sheet iron 
piping to burners discharging over the fuel bed. These burners are usually 
attached to a length of pipe, the upper end of which is carried by a ball joint, 
and the lower end latched to the burner. Y-branches or switches allow of 
one cyclone separator feeding several boilers. The piping from the separator 
should not slope more than 30° from the vertical. 



134 



FURNACES AND SETTINGS 



If dry chips and shavings are to be fed to the furnace, or if a mixture 
of wood and coal is to be burned, the resulting high temperatures may burn 
the lirebrick. But if the amount of heat absorbed directly from the fire is 
increased by the use of the standard setting, Fig. 60, the furnace temperature 
will remain normal. The necessary cooling effect is obtained by the arrange- 
ment of the baffles. Near the front header the underside of the tubes is 








Fig. 59. Burning Wood Refuse Carried by Pneumatic Conveyors. 



FURNACES AND SETTINGS 



135 



exposed for a short distance, while the rest of the first row of tubes is 
encased in baffle tile. The gases are directed upward against the tile roof, 
then over the top of the wall and under the deflection arch. The air and 
gases are thoroughly mixed and smoke formation prevented. 




Fig. 60. Setting for Burning Coal and Wood Mixture. 



FURNACES AND SETTINGS 



137 



For burning bagasse a special extension furnace is required for 
combustion. These wet fuels should be burnt on hearths at the bottom 
of high reverberatory chambers as shown in Figs. 61 and 62. The raw 
material is fed in from the top, and is dumped directly onto the fire, so that 
the fuel bed is generally in a thick pile. The necessary air is brought in 
through the tuyeres under light pressure. Combustion is completed in return 
flues, which carry the gases to the boiler. 




'%3ffE*!EC 



Fig. 61. Preferred Setting for Burning Bagasse. 



Oppositely inclined grates converging downwards may be installed near 
the bottom of the furnace. These can be automatic or hand-operated. 
One furnace can be used for two boilers, by setting it between them. 




o 

m 

■i-i 

03 
V 

X 



u 

C 

(4-1 
O 

Jii 

o 

CO 

cs 

G 
O 
<M 

C 

6 

V 

O 

6 
u 



4-> 

g 
U 



V 



FURNACES AND SETTINGS 



139 




Fig. 62. Alternative Settings for Burning Bagasse. 



Waste Heat Settings 

CERTAIN manufacturing processes depending on the direct combustion 
of fuel are inherently inefficient when considered from a thermal stand- 
point The term efficiency, as applied to these various processes, has the 
same significance as it has when applied to the operation of a direct fired 
<;team boiler. In boiler practice the object is to utilize every available B. t. u 
for the generation of steam; but there are certain unavoidable heat losses ot 
which the greatest is the heat carried away by the stack gases. 
^ In some industrial burning operations the thermal efficiency is not above 
40 per cent. That is to say, the number of B. t. u. actually utilized in the 
melting smelting or treatment of the material involved, is only 40 per cent 
of the number of B. t. u. actually supplied to the furnace as fuel. In these 
operations, as in steam boiler practice, the largest thermal loss is the heat 
carried away by the waste or stack gases. 

In order to increase the efficiency of the primary furnace, waste heat 
boilers are installed, which generate steam for pknt use This steam is a 
direct saving. With the ever increasing price of fuel, the mstallation ot 
waste heat boilers is decidedly advisable wherever conditions permit. 




o 

in 



OS 

V 

X 



08 
V 

G 

'C 
X 

o 

o 



"S 
■« 

•4-) 

c: 
o 
(J 

6 

CO 
V 



O 

1) 

a 

O 

6 
O 

c 

V 

e 

a 
O 

•O 

c 

csl 



O 

a 
& 

V 



O 

V 

a 

CO 

O 



FURNACES AND SETTINGS 141 



The operation of the followmg types of furnaces with their relatively 
low thermal efficiencies, is in general such that waste heat boilers can be 
profitably installed. 

Open Hearth Steel Furnaces. 

Rotary Cement Kilns. 

Puddling Furnaces. 

Malleable Iron Melting Furnaces. 

Forge Heating Furnaces. 

Bee Hive Coke Ovens. 

Coal Gas Benches. 

Oil Stills. 

Zinc, Copper, Nickel, etc.. Refining Furnaces. 

Soda Ash Furnaces. 

Glass Melting Furnaces. 

Waste heat boilers cannot be conveniently installed with every such 
furnace, because raw materials, fuels and operating conditions differ so 
widely that each proposed installation requires individual study to determine 
the feasibility of a waste heat boiler installation, and the best method of its 
application. 

Inasmuch as the temperatures of waste gases available for waste heat 
boilers vary from below 1000° F. for long cement kilns up to 2200 for melting 
furnaces, it is obvious that there can be no set or standard proportion of 
boiler heating surface. With gases around 1000° F. the heat transferred 
to the boilers by radiation is almost negligible and the steam is generated 
principally by convected heat. Where the gases are at temperatures above 
2000° F. the radiation is appreciable, approaching that of a direct-fired boiler. 
Hence a boiler for high temperature waste heat work varies but little in 
design from a standard direct-fired unit. 

The m.ajority of waste heat boilers in service are utilizing gases at 
temperatures ranging from 1100° to 1600° F. In this class steam is generated 
by convected heat and therefore the arrangement of heating surface and 
baffling departs materially from the standard for direct-fired work. 

The transfer of heat by convection follows certain laws, of which cog- 
nizance is taken in the design of Heine waste heat boilers for relatively low 
temperature work. As early as 1874 Professor Osborn Reynolds developed a 
law of convection, which has been later substantiated by such investigators 
as Nicholson, Jordan, Stanton and Fessenden. This law states that the rate 
of heat transfer bears a certain definite relation to the velocity with which 
the gases sweep over the heat absorbing surface. Or stated in different 
words — the B. t. u. transferred per square foot of heating surface per 
hour per degree difference in temperature between gas and water increase 
with increasing gas velocities. Therefore, in a waste heat boiler of the 
convected heat type, in order to obtain a satisfactory rate of heat transfer 
and to keep the heating surface within reasonable limits, the gas velocities 
employed are considerably higher than in direct-fired practice. 

The first modern high gas velocity waste heat boiler was a standard 
Heine boiler installed in 1910 by C. J. Bacon at the South Chicago Works of 
the Illinois Steel Co. The gas velocity in this boiler was equal to 5300 lbs. 
of gas per square foot of gas passage area per hour, and established the 
high limit up to the present time. 

High gas velocities, which generally run from 2500 to 4500 lbs. of gas 
per hour per square foot of average gas passage area, are obtained in the 
Heine waste heat boiler by various methods of baffling. In instances where 
the gases are comparatively free from dust, horizontal baffling is employed. 
This is easily installed and replaced, and readily rearranged, should it be 
desired to increase or decrease the gas velocity in order to alter the rate of 
heat transfer. 



142 FURXACES AXD SETTINGS 

In instances where the gases are burdened with dust, which would 
accumulate on horizontal baffles, there are emploj-ed other methods of 
baffling which maintain a high gas velocit}- and allow the dust to fall clear 
of the tube bank. Several dift'erent types of baft'ling are used in Heine 
waste heat boilers, and these make such a varietj- of possible arrangements 
that no tA'pical illustration can be given. The dust falls into hoppers built 
integral with the setting and equipped with air tight cleanout doors. 

Due to the high gas velocity employed, there is an unusually high draft 
loss through the boiler, which is taken care of by induced draft fans. Fans 
have a steadying effect on the draft at the primary furnace, and when so 
desired the draft at the furnace may be increased wnth increased furnace 
output. It is desirable that the fans be driven b}" a variable speed motor 
or steam, turbine, so that any variation in the quantity' of gas may be satis- 
factorily handled. 

In plants where the temperature of the waste gases approaches that of 
direct-fired practice, or where the conditions do not warrant the expense of 
an induced draft fan installation, it is customary to use a single pass waste 
heat boiler and to employ- natural draft. The boiler is then verj- similar 
in design to a standard direct-fired unit. 

It is generalh- preferable to install waste heat boilers in connection with 
continuously operated furnaces. If the furnace is operated only part of 
the time, it is customar}- to install auxiliary grates under the boiler and to 
fire coal directly, when the boiler is not being supplied with waste heat from 
the furnace. 

The necessity of having tight settings is continuously brought to the at- 
tention of direct-fired boiler operators ; but in waste heat utilization this 
requirement is even more important, for there is a greater vacuum in w^aste 
heat settings, and hence a greater tendency for air leakage through crevices 
in the brickwork, around loose doors, etc. The waterleg construction of the 
Heine waste heat boiler is such that one continuous surface is presented at 
both the front and rear of the setting. There are no separate headers and 
therefore no crevices to caulk with asbestos rope, which quickly becomes 
brittle, often drops out, and thus increases the air leakage. The soot blower 
elements project through the hollow sta3-bolts of the front and rear waterlegs, 
so that it is not necessary to place dusting doors in the side walls. The 
fewer the openings in the setting brickwork the more durable it is and the 
less the tendency for air leakage. All cleanout or access doors should be 
provided with gaskets to insure tight closure. Steel casings for waste heat 
boiler settings are not altogether satisfactory, because cracks are likeh' to 
develop in the brickwork, and being inaccessible behind the casing are hard 
to detect and repair. Asphaltic compounds suitable for painting the exterior 
of the brickwork are satisfactorj- for reducing air leakage. 

One fact in the design of a complete waste heat boiler installation should 
be constantly borne in mind, — tlie operation of the boiler must in no way 
interfere with the operation of the primar}- furnace to which it is connected. 
Bj-pass flues and dampers must be arranged so that in case something un- 
foreseen happens the gases of combustion can either be passed up the 
stack or to another waste heat boiler. Where there are two or more boilers 
utilizing the waste gases from two or more furnaces, it is desirable, where 
space or operating conditions permit, to arrange one common fine into which 
the waste gases from all furnaces discharge, and from which branch flues 
lead to as many boilers as are necessar\- to handle the gases satisfactorily. 
With this arrangement the dampers can be placed so that any desired flexi- 
bilit>' of operation is obtained. 



FURNACES AND SETTINGS 



143 



Marine Settings 

IN shipping practice boilers of compact design and light weight are re- 
quired so that the cargo capacity will be a maximum. Only water-tube 
boilers fulhll these requirements. 

For cargo carriers and other steamships, boilers, Fig. 63, are supported 
by a steel structure secured to the framing in the vessel. On this structure 
is a steel-plate casing, which encloses the entire setting. Inside of the casing 
is insulating material, faced with firebrick. This construction insures pro- 
tection against high temperatures and minimizes the radiation and infiltration 
losses. 




Fig. 63. Heine Marine Cross Drum Boiler. 



For dredge boat service, the setting is bunt itij of lirel)rick, hollow tile, 
asbestos and sheet iron. All parts of the furnace interior exposed to high 
temperatures are lined with firebrick. Back of this is the tile, which is 




Front View of Marine Casings for a Battery of Two Heine 
Cross Drum Marine Boilers. 




Rear View of Marine Casings for a Battery of Two Heine 
Cross Drum Marine Boilers. 



FURNACES AND SETTINGS 



145 



covered with asbestos on the outside. The sheet iron encases the entire 
setting, as shown in Fig. 64. The boiler itself is carried on steel supports at 
the front and rear, while the breeching and stack are carried by structural 
framing. 

Separate Heine publications dealing with marine boiler practice are sent 
on request. 




Fig. 64. Heine Dredge Boat Boiler Setting. 



Boiler Setting Requirements 

THE essentials of a boiler setting are a firm foundation, proper distribu- 
tion of brickwork and steel supports, adequate furnace and ashpit space, 
and insulation against heat losses. The furnace proper and masonry parts 
included in the furnace should be made of materials that will stand severe 
service and high temperature with the least maintenance. The refractory 
material should be combinations of fire-clay, or else special firebrick. _ 

The boiler must be supported on a solid base to prevent settling and 
cracking of the walls. A weak base may impose severe strains upon the 
boiler piping, resulting in sprung and leaky joints and ruptured connections. 

The soil is the determining factor in proportioning the foundation. In 
soft ground under a large boiler, it may be necessary to drive piles or to lay 
a concrete base at least 2 ft. thick over the entire space occupied by the 
setting. The walls are started on this base or a concrete foundation with 
footings is laid to receive the brick and steel structure. The depth of 
foundations and width of footings then depend upon the size of boiler. 

The side and end walls of a boiler setting should not be less than 12 in. 
thick. In older designs, a 2-in. air space was generally provided. It was 
thought that the double wall preventied heat losses and also cracking due to 
expansion. Tests by the U. S. Geological Survey indicate that an air space 
is of little value in setting walls. The radiation losses appear to be greater 
for a wall with an air space than for a solid wall, especially if the air space 
is near the furnace side. 



FURNACES AND SETTINGS 



147 



While concrete has been used in several installations, the walls of the 
setting, as a rule, are made of well-burned red brick. These should be laid 
true and in high grade mortar, consisting of a thorough mixture of one part 
Portland cement, three parts unslaked lime and sixteen parts of clean sharp 
sand. Each brick should be solidly imbedded and the joint fully filled. 

Ordinarily, the furnace, ashpit, bridge wall, arches and floor of the 
combustion chamlier are built of red brick. All parts of the brickwork in 
contact with the hot gases or exposed to the flame, should be faced with 
or else built entirely of firebrick capable of withstanding the high tem- 
peratures. 

The firebrick should be highly refractory and should be mechanically 
strong and sound so that it will not spall, flake or crumble. Firebrick 
linings, walls and arches must be given reasonable care. They should be 
laid in fire-clay mortar having the same properties as the brick itself. Flux- 
ing material, such as lime, should not be used in making the joints. Fig. 65 
can be used in estimating the number of brick required for standard water- 
tube boiler settings. 



o 
"l 

CD 

15 
q: 

o 

V) 

c 



(0 

O 

X 




100 



200 300 400 500 

Boiler Rating in Horsepower 

Fig 65. Approximate Number of Brick Required for 
Standard Heine Boiler Settings. 



GOO 



o 

L 
CD 



o 



148 FURXACzs a::i szmxGS 



The lurriace construction can be ma if =:r:: rer :r ~:-r d'jrable by 

using special blocks in place of the star : i - r : : ^^ 7 T.t : :cks are 

??.-rer irz therefore reduce the number : :- :t: :ti Z :he use 

:: : - .: refractorj, a one-piece, con: : . : :i. :.:..:...: .:: :: .r can 

f . . .: :...:5 eliminating all joints. 

7 T 7 5 s i-dd be strengthened by steel channel buck-stays placed 
:.: 7 : tt 1 : : e -etting and at several points along :he siies These 
5 7 e -e: T :: :Jie walls bv longitudinal and transerre i":h:- ri? 






Other structural members are rr :t_ - : e 
:ir number and distribution depending upon :-.e 
^e of furnace. 



Refractory Materials 



T 



i : _ ^^ ^ T ;T':^rure5. acncn :: t : ^.ses : ;i ne inii. 

izrciics ^nc ;: me n : :r and adding :: : . :: : \e nre. Tne rein :: r t? 
for boiler furnaces :' bricks. r ; ecial forms, ani ; t. 

F:-e r'ay (a mixture :; sh ;i anf a!n~ in ::::? :ne ^asis of mos: ::: - 
: ' aterials. Ac: ' r :: _ .. - : -:: ;7; is used eittt: r 

: ; ; : - n: : - t : - : :: r n : : : Z: : her and r^i f: n 

!:^ : :t t: : :t: : _ :: : ii 7: : : : : : : :: is :.z^ : . 3ther re:: :: ::y 
n:a::er sirh as bauxite n i^ esia, to lend plasticity. 

Tire :7iy5 are divi t_ : : :■ classes: flint clay and plastic clay, the 
:' ri::Tr iT.ng the harder : :i i: re r.early chemically pure. Flint clays are 
:t - :r mottled n : ; n Plastic &re clays vary in colzr :r:n: 

It : i:.:. inchidnn ^ri r nd olive. The plastic is aiiei :: 

: e r : mj- to incre ne : e n generally at the cost oi its 

rrin i: r less. Commer : i. r.re i.:. i : - many impurities, and the color 
7- n : . 5 -:e r^^ide to its quaiir. . 

T:er 7; srch as silica, baoxiie, chrome, ms.^::es :e and dolomite have 
r : ^ . "^ : ^her than fire clay, but have n;: ;r:ved satisfactory in 
: r r ;: :: T.rese materials do not withsrsni sniien heating, cooling. 
; r T : r e : : n : : the gases and ash. 

T :e : _ : : n rain in a coal furnace, according to JVm. A. Heisel. 

are i: :i : r t t ' : r.z life and general use of silica brick. With an oil 

r ^if - 7 : T ^ T ~: re. as far as chemical action goes, but the 

e ne T : nr :rrr r : f re :: sadden starting or stopping cause 

r ; e ; ii T.-rr :i : : ^: f::..nig or the breaking off of large 

7 : xite brick, according to A. D. Williams, cost two to three times as 

: --e clay or silica brick. They are hard and tough, cinder does 

r : :: them: and they last longer than silica brick when exposed to 

- . However, bauxite :enis :: s;s.7 and break off when suddenly 

At high pressures :. e ;er?.:rre5 ;/;''; 'rr 2nd magnesite brick cannot 
withstand the strain f . :_ i :r : r^ md cooling, so that they have not 
found favor except r sir.; i: z:_7r r^.-l operations. 

Fire Brick 

PLASTICITY, accordii^ to JL 5. Marks, is considered the mam factor m 
^elertion of fire brick. It indicates the tendency of a bride to tHgoeMne 

temperature lower than its melting point and to become deformed 

^ en load- Under a unit stress of 100 lb. per sq. in., the plastic point 

re than 2400 d^-, otherwise the brick is not suitable for 

boiler :r :_ ^.z:. 



FURNACES AND SETTINGS 



149 



Fusing point is the temperature at which fire brick will fuse. A high 
value ordinarily indicates that the critical temperature, or that of plasticity, 
is correspondingly high. 

Expansion represents the tendency of the brick to change in size with 
change in temperature. Lineal expansion of from 0.01 to 0.08 in. in a 9-in. 
brick is the permissible limit for furnace construction. 

Compression is measured by the strength or load necessary to cause 
crushing at the center of a A%-'m.. face, by a steel block 1-in. square. 

Hardness indicates the brittleness of brick and its tendency to crumble ; 
it is ordinarily estimated on an arbitrary scale of 10. 

Ratio of nodules expresses the percentage occupied by flint grains in a 
given volume. The scale is : high, 90 to 100 per cent ; medium, 50 to 90 
per cent ; low, 10 to 50 per cent. 

These nodules are the average size flint grains found in a carefully 
crushed brick. Small nodules are the size of anthracite rice ; large nodules 
are the size of anthracite pea. 

These characteristics are summarized in Table 6, for the three classes 
of -first-grade or No. 1 brick. Class A brick are suitable for stoker settings 
operated at high overload or for other extremes of operation. Class B brick 
are used for furnaces of stoker-fired boilers operating at normal load, and 
for hand-fired boilers under overloads. Class C brick are recommended for 
standard boiler settings, for occasional short overloads. 



Table 6. 


Properties of Commercial Fire Brick 






FIRST GRADE (No. 1) 


No. 2 


Characteristics 








Grade 




Class A 


Class B 


Class C 




Safe Fusion Point, deg.. 


3,200-3,300 


2,900-3,200 


2,900-3,000 


2,400-2,700 


Compression, lb. per sq. 










m 


6,500-7,500 


7,500-11,000 


8,500-15,000 


14,200-32,000 


Relative Hardness 


1-2 


2-A 


4-6 


6-10 


Size of Nodules 


medium 


medium to 


medium to 


small to very 






medium large 


large 


small 


Ratio of Nodules 


high 


medium to 


medium low 


low to very 






high 


to medium 


low 



The figures in Table 6 indicate that the better the brick the softer 
it is. It should not be any harder, therefore, than is required for the 
necessary strength. The unequal expansion and localized stresses due to 
sudden temperature changes often cause failure when the fire brick is 
hard and brittle. 

The melting temperatures of refractory brick, as determined by C. W. 
Kanolt, are given in Table 7. The temperatures do not indicate the fit- 
ness of the material .for use in boilers, because the erosion, crushing strength, 
ability to withstand sudden load changes and to resist fluxion, must all be 
considered. In stoker-fired boilers temperatures of nearly 3200° F. have been 
obtained, although the melting point of chemically pure fire clay is only 
3326 degrees. 



IdO 



F I' R X A C E S A X D S E T T I X G S 



Table 7. Meltinz Points of Fire Brick 



Brick 



Temp^ Deg. 



Fire Clay 

Silica 

Magnesia. 
Bauxite. 

Chromite. 



2.732-3.1S2 
3.092-3.182 

3902 
2.912-3.272 

3.722 



A simple quaiiiy test is niaue oy ureaKiing tiie uncK. in a low graae 
brick the fracture will be fine and uniform, like bread. In a better qualit>- 
brick the surface is open, clean, white and flinty. 

Fire brick 9-in. long are considered standard. ^lanufacturers carr>- a 
stock of the shapes and sizes shown in Fig. 66. Special sizes can sometimes 
be purchased from stock, but usually have t-:^ be made to order. 




Straight Brick. 




Small Brick. 




Split Brick. 




2-inch Brick. 




Soap Brick. 




No. 2 Wedse. 




No.i Ke> 




No.l Neck. 





No. 4. Key. 




No. 2 Neck. 





Jamb. 




End Skew. 




Feather Edge. No. 3 Arch. Circle Brick. 

Fig. 66. Some Standard Fire Brick Shapes. 



FURNACES AND SETTINGS 151 

Table 8 gives the weight of different refractories, as brick and as mortar. 
Table 8. Approximate Weights of Refractories 



Material 




Mortar or Cement, 
Lb. per Cu. Ft. 



Common Clay. 

Fire Clay 

Silica 

Chrome 

Magnesia 

Plastic 



100 
150 
128 
175 
160 
120 (Solid) 



78 

85 

75 

135 

127 



Influence of Ash. Refractory materials may deteriorate because of the 
chemical action of the fused ash and of the gases. Certain constituents of 
ash, according to E. G. Bailey, influence the fusibility of the fire brick. 
In one installation, where the furnace lining gave trouble, the fusing tempera- 
ture of the fire brick was 3100 deg., and that of the ash was 2600 cleg. ; 
the chemical action of the combination caused fusion at 2400 degrees. Ash 
from other coals would not have melted the fire brick used; other brick 
and the same ash might not have so materially affected the melting point. 

Mortar and Cements. Many arches and walls seem to have failed 
liecause the mortar used in making the joints melts and allows the brick 
or blocks to fall. The mortar used should be of practically the same 
composition as the brick itself. For fire clay brick, finely ground fire clay 
mortar should be used ; silica cement for silica brick ; and magnesia cement 
for magnesia brick. 

The fire clay mortar should be of the first quality, otherwise it will 
melt and run long before the brick. Common sand, salt, or lime, hasten 
fusion, and cement the brick thoroughh^ but at high temperatures this 
fusion destroys the brick prematurely. Tests by Raymond M. Howe 
show that the addition of only 5 per cent of Portland cement, asbestos or 
salt lowered the fusion point of fire clay almost 400 degrees. On the other 
hand, fire sand, which is calcined clay or fire brick in powder form, can be 
added to the mortar and prevents shrinkage of the raw clay and crumbling 
of the joints. This shrinkage can be prevented, and a firmer joint estab- 
lished, not by adding foreign materials to the fire clay, but by using the 
same material, taking the precaution, however, that a certain amount of 
clay has previoush^ been shrunk. 

Several commercial cements withstand temperatures as high as 3100 
deg., and are recommended for use with high grade fire brick. 

The trend of opinion favors furnace walls of as few different materials 
as possible ; these must be selected carefully, even though solid fire brick 
are to be used. The use of two grades of brick, rather than one. may be 
preferable and economical, especially as the burden on side walls and 
on an arch is different. Side walls for coal fuel, states Heisel, generally 
require a refractory less porous and soft than would be used in an arch, to 
withstand the abrasion caused by the fire tools, and the cutting caused by 
breaking or removing the clinkers. 

Furnace walls are safeguarded and the lining preserved by devices 
which supplv air to the walls and thus prevent clinker from adhermg 
to them. This reduces the temperatures without reducing the furnace 
efficiency. Perforated refractory blocks. Fig. 67, are used for the lining 
in the lower parts of the side walls, bridge walls, and wherever the action 
is most severe. Air is admitted through holes in the wall blocks. The 
holes are connected by ducts to the fan draft system. With underfeed 
stokers, these blocks may materially increase the life of the hnmgs. 



152 



FURNACES A X D 



\* 



,-^_ 



— ^ 



Air Dud 



Air Duct ^ 

wiih Samper 



r'/^^j 




Damper 

-+©' Rod 




Longitudinal Section. 

Fig. 67. Refracton.' Blocks for Ventilating Furnace Walls 



With standard brick the joints and parts to lay are so numerous that 
blocks are made for door arches, furnace walls, and bridge walls. The 
blocks are keyed or have a tongue and groove, and sometimes are machined 
to insure a good fit. It is said that one 24-in. block takes the place of 40 
standard brick, and reduces by more than two-thirds the running inches in 
the joints in the face of the wall. 

In place of the blocks, so-called plastic fire brick is used for boiler 
settings. This is a moist plasric mass, compounded of fire clays mechan- 
ically treated so that expansion is practically eliminated. The plastic 
refractory is placed by hand and pounded so that the front arch, side and 
front walls, bridge wall, or combustion chamber lining is one continuous 
structure. This material, it is said, does not break or spall under varying 
furnace temperatures. 



FURNACES AND SETTINGS 



153 



Arch Construction. All brick in the same row should be of even shape 
and thickness, this applying, states Heiscl, to arches particularly. The vari- 
ation in size should not exceed /4-in. in a maximum length of 9 inches. The 
dry brick selected should be tried over the arch form, and those of uneven 
thickness should be cut and rubbed to avoid large mortar joints. Wedges 
should be used to keep the brick bottom in even contact with the arch form. 
The key course should be a true fit from top to bottom and should be driven 
from 1 to 1^ in., depending upon the hardness of the brick and the width 
of the arch. 

Suspended flat arches are sometimes used instead of tlie ordinary sprung 
arch. Fig. 68 shows a double suspension arch, about 3 in. deeper than the 
ordinary single arch. A so-called reserve arch is placed above, and supports 
the lower arch. An air space is provided between the two arches. If a 
burn-out occurs, the upper arch protects the supporting beams until the 
boiler can be shut down and the damaged blocks replaced. The new parts 
are slid into the grooves of the reserve arch. 




Fig. 68. Liptak Type of Suspended Flat Arch. 



Radiation and Leakage 

COMMON brick is somewhat unsatisfactory for boiler settings. As it is 
not a refractory material, it is always protected from high temperatures 
by a lining of firebrick. It is a poor heat insulator; it is porous and permits 
considerable infiltration of air, and it cracks easily, especially around openings 
such as dusting doors, and allows further air inleakage. 




Front View of 500 H. P. Heine Standard Boiler set over 
^Westinghouse Underfeed Stoker. 



Fl^RNACKS AND SETTINGS 



155 



Insulating material will decrease heat loss to a consideral)le extent. 
Siliceous insulating material may be cut into blocks of standard firebrick 
size which have sufficient strength to be laid as a core wall between the 
fireback furnace lining and the outer red brick course. Such a wall is shown 
in Fig. 69. 



2500^ 



Fire Sr/ck-'.^y 



,Common 
' Brick 




2S000 




Brick 



/nsu/afina 
Brick 



Common 
Brick 



Plain Wall 



Insulated Wall 



Fig. 69. Heat Flow Temperature Gradients in Brick Wall. 



The insulating brick should be at least 4^ in. thick. It should be laid 
with broken joints and in a mortar made of material having the same 
characteristics. The temperature drops through a standard boiler wall and 
an insulated wall are compared in Fig. 69, by A. L. Gossinaii. 

Metal wall ties are used in bonding or else firebrick, insulating l)rick 
and red brick are tied into a solid wall by brick headers staggered in at 
intervals. 

Fig. 70 shows the thermal conductivities of refractories and insulation, 
the measurements being made on slabs one inch thick and one square foot 
in area. 



156 



F U R X A C E S AND S E T T T X G S 



The insulation reduces the radiation loss, but on account of the joints 
in the brick setting the air leakage is not eliminated. To offset the infiltra- 
tion only, states /. Harrington, a glazed or vitrified brick, laid in cement 
mortar, gives a hard and durable wall, but the heat transmission is high. 
A boiler setting encased in sheet steel is practically air tight, but the steel 
has no insulation value. 



12 



10 



r9 






b7 

c 
C 

X 

a 



u- 5 
a. 



■*^ 3 

































y 


y 


































^/ 


y 












1 

i 




















y 


y 










y^ 


y 
























/ 










y 


y 


_^ 


^ 


















r 










~p^^ 




^ 




















y 


f 








,y^ 


A 


^ 


*^ 




















> 


k' 








^ 


M 


>^ 
























M 


/ 






-tH 


^ 


^ 
























y 


y 






^ 


:::^ 


:^ 






















>^ 


/^ 




c^ 


y 


y 






























,j 




> 


/ 


^ 


































y 


^ 


































y 














1 1 I 1 1 

a = Silica Brick, 97.3»/cu. fi 
b 'Quarfzife,//9*f/ca.f-/- 
c -All Fire Clay,li9*/cu.ft 
cl= Insulafinci Brick, 27-3C 


L 










i 
















































1 
1 














l^cu.ff. 








































1 




















































































1 








1 








1 i 


1 
1 




1 


1 




1 






























1 1 




1 

1 




































L^ 












— { — 























































200 



400 



leoo 



GOO 800 1000 1200 1400 
Temperature Difference, Degrees 

Fig. 70. Heat Conductivity of Brick, One Inch Thick 



1800 2000 



F IT R X A C E S AND SETTINGS 



157 



Radiation and infiltration losses are both eliminated by applying asbestos 
or magnesia on the outside of the setting walls, and then encasing the whole 
with sheet steel. This construction is expensive and carries the objection that 
cracks in the brickwork are difficult to detect or repair. 

A less costly construction, which also reduces both losses, is described 
by E. S. Hight. The details are shown in Fig, 71. The saving effected by 
this insulation is said to be sufficient to repay the first cost in less than six 
months, providing the boilers are operated at full load 50 per cent of the 
time. Wire loops are inserted into the red brick of the setting wall, so 
that they overhang at every fifth or sixth course. After the wall has been laid 
up, a Vi6 in- finish (two or three coats) of coal tar is applied. This should 
be boiled to a thin consistency and have asbestos wool stirred into it. After 
the mixture has dried a plastic asbestos paste or cement is applied to a 
thickness of about V/4 inches. Over this a ' wire mesh is stretched and 
fastened to the protruding loops by small wire clips. Then another ^-in. 
layer of asbestos cement is applied. When the plastic mass is dry, the 
surface is covered with 10-oz. duck or canvas. This is pasted down tightly 
and the edges are fastened by wires or metal strips to the steel work of 
the setting. The duck is finished with two coats of asphalt paint or varnish. 




\i^%— Asbestos Cement 



-Wire Loop 

10 oz. Duck, with 
(2 coats aspha/fum 



**6W/'re~. 



Fig, 71. 



%-2"Chicken Wire 



^.Coai Tar and 
Asbestos 




£ric/<- 



Scttinq Wire 
Loop inwlacc 



Inexpensive Method of Protecting Setting Against 
Radiation and Infiltration Losses. 



For the covering of boiler tops and drums, insulating brick have been 
found most desirable. This can be strengthened by a course of common 
brick and then a 2-in. topping of concrete. 



159 



CHAPTER 5 



MECHANICAL STOKERS 

THE advantage of automatic stokers as compared with hand firing lies 
mainly in the more efficient combustion of the fuel, the elimination of 
smoke and dirt in the boiler room, and in the ability to drive boilers at 
high rating. In large plants where automatic coal and ash handling equip- 
ment can also be installed advantageously, the use of stokers reduces the 
labor cost and the labor difficulties. The emission of smoke, except for 
brief periods, is forbidden in many cities ; and when smoke is eliminated, the 
general efficiency of the boiler plant is usually increased. With stokers the 
fuel is fed and the air supplied uniformly; no fire doors need be opened 
to chill the boiler and dilute the stack gases ; thus combustion is most 
thorough even with poor fuel, at combustion rates that produce the highest 
steaming values. The grade of fuel influences the choice and design of 
a stoker, but when it is difficult to secure coal from the same source con- 
tinually, the load conditions are even more important. A plant that must be 
operated frequently at 300 or 400 per cent of rating must necessarily lie 
equipped with stokers that can be driven at corresponding rates, with forced 
draft, regardless of the fuel available. When the load conditions are more 
nearly uniform, the stokers can be of lower forcing ability, and those best 
suited to the coal available can be chosen. 

The following illustrations are given as examples of the types classified . 



Overfeed Stokers 

TN overfeed stokers the coal is generally burnt on sloping grates. The general 
■'-position of these is fixed, but reciprocating grate sections gradually work 
the burning fuel down to the ash receiver. The coal is fed from hoppers 
adjoining the upper part of the grates and passes first over a coking section, 
where the volatile gases formed are burned by the aid of secondary air. 
Overfeed stokers are used with a wide variety of fuels, and boilers are 
operated up to 200 per cent of rating without overheating the grates. 

Cleveland Stoker, Fig. 72. The coal from the hopper is pushed in by 
feed plates and pokers, so arranged that by increasing the speed of the 
rectangular feed plates the depth of the fuel bed can be increased. The 
draft is adjustable for the particular coal used; the three dampers in the 
wind box below the grates distributing the required air. The entire unit 
is shipped assembled, and runs on tracks so that it can be removed to gain 
access to the setting. 

Detroit Automatic Furnace, Fig. 7Z. Coal is fed to the magazines by hand 
or from chutes, and is driven to the coking plate by pusher boxes, from 
which it slides down the grates to the clinker grinder, where a supply 
of exhaust steam softens the clinker. Air for combustion is supplied at a 



STOKERS 




' >'. **".« .'-'*.-».'> ■ 3''<l V' .• '* "-^ ' ' ■ ■<». ' ' ".^ ■ ' ■" ^ •' '^ ^ •"»'•■ J '•;'.• 



a ■ ' , 3 . • <) • 



Fig. 72. Cleveland Overfeed Stoker. 

number of points — that entering through the upper dampers being heated 
between the furnace arches and entering the furnace at the arch boxes, 
in addition to that which passes through the grates. 



^%ii 




Fig. 73. Detroit Automatic Furnace. 



STOKERS 161 

Model Stoker is also of the self-cleaning, side-feed type. The grates 
slope to the center and are in pairs, set on edge, with a small surface exposed 
to the fire and a large surface to the cooling action of the entering 
air. Every alternate grate is movable, the upper end being hinged to the 
stationary grate, while the lower end is rocked by a moving bar ; the burn- 
ing fuel is moved down by this bar, and the fine ashes are dropped. Both 
the feed and the speed of the crusher bar at the bottom can be varied to 
suit operating conditions. The stoker has been used with mine refuse con- 
taining 30 per cent of ash. Natural draft can be used, or an induced suc- 
tion of 0.2 in. at the fire chamber; with 0.4 in. it is claimed that the boiler 
can be driven at 300 per cent rating. 

Westinghouse-Roncy Stoker. The grates are horizontal, arranged in 
steps, and rock backward and forward, gradually passing the coal to 
the lower part of the slope. The coal is fed to the coking plate at the 
top by the hopper plate outside, and ignition is helped by the arch above. 
The guard between the combustion grate and the dumping grate is lifted 
when the ashes and clinker are dumped. This stoker operates on natural 
draft, 0.25 to 0.6 in. at maximum load, and has a reserve capacity of 200 
per cent of rating. It is used for both high fixed carbon and high volatile 
coals, at maximum combustion rates of 35 to 50 lb. per sq. ft. per hour. 

Wetzel Stoker. Moving coking grates are placed immediately behind 
the hopper. Main grates extend down to the dumping grates. The bars 
of the main grates are alternately stationary and moving. The openings 
in the coking grates are large, supplying air for the combustion of the volatile 
in the space above ; the holes further down are smaller, while those in the 
lower part of the main grates and in the dumping grate are still smaller, 
supplying just enough air to burn the remaining solid combustible. For 
loads less than 200 per cent of rating natural draft is sufficient. 



Underfeed Stokers 

IN THE underfeed type fresh coal is fed from below the fuel bed by 
some form of pusher, is gradually forced to the upper zone, and toward 
the ash dump. The fuel bed consists of three layers, a lower one of green 
coal, next a layer of coal being coked, and an upper or incandescent zone, 
in which the fixed carbon is consumed and the volatile gases from the coking 
coal underneath are mixed with air and ignited. The action is similar to 
that of a gas producer, except that in the stoker the combustible gases pro- 
duced are consumed within the furnace. Underfeed stokers have been suc- 
cessful in large plants for as high as 400 per cent of boiler rating. 

Combustion "Type E" Stoker. A central retort extends back horizontally 
from the hopper; grate bars adjoin it at the top, on both sides. The bars 
slope slightly toward the outside dump-trays. The coal is pushed into 
the bottom of the retort, raised to the grate bars by pushers, and worked 
toward the outside by reciprocating rocker bars in the grate. Each unit is 
operated, and can be banked or forced, independently. Air is fed in through 
a central wind box under the retort, and through the ventilated grate bars ; 
the fan speed is controlled by a damper regulator responsive to the steam 
pressure, while the supply of coal is controlled by adjusting the number of 
strokes of the pusher. The stoker is recommended for semi-anthracite, semi- 
and sub-bituminous coals. The wind box pressure should be from 1 to 5-5 
in., say 1 in. per 10 lb. combustion rate, and the suction at the fuel bed is 
0.05 in. Boilers can be driven at 225 per cent continuously, and at 300 per 
cent or more of rating, for several hours. 



162 



STOKERS 



Jones Stoker, Fig. 74, A series of retorts are inclined slighth" to the 
Lack of the hoppers. A steam cylinder operates a pusher rod, which feeds 
a charge of coal and forces the preceding charge of green coal backward 
and up. The coke on top and the volatile gases formed below are burned in 
the upper incandescent zone. The balanced dump plate is dropped to remove 
accumulated ashes. Air under pressure is supplied to tuyeres at the dead 
plate, and other points in the furnace. The rates of suppl}- of air and coal 
can be varied by hand, or are automatically controlled by the steam pressure. 



Alkllii i i 




Fig. 74. Jones Automatic Self-Cleaning Underfeed Stoker. 

Moloch Stoker, Fig. 7S. The horizontal retorts are fed by a steam ram. 
Air is admitted through the tuyeres in the upper part of the retorts. In the 
larger units clinker grinders are placed between the retorts and remove the 
refuse automatically. The stoker is used for bituminous and semi-bitumin- 
ous coals. Fair ratings can be developed with 0.30 to 0.45 in. natural draft; 
with forced draft of 3.5 to 4 in., practical!}' any desired rating can be main- 
tained. 



,1 J, 



J' ,iV ,1 (If-'" I' ■' 




{ w m 





Fig. 75. Moloch Self-Cleaned Underfeed Stoker. 

Roach Stoker, Fig. 76, has a ram-fed central retort, live and dead grate 
bars sloping awa}- from it on each side. Part of the air is supplied through 
the bottom of the retort, while that to the grates is regulated b\- several 
gates. Refuse is removed by dump plates at the side of the grates. 



STOKERS 



163 




Fig. 76. Roach Underfeed Stoker. 

Stevens Stoker. Screw conveyors force the coal through horizontal 
troughs. The space between the troughs is filled by rocking grates, set flush 
with the tops of the troughs. Full boiler rating is developed with 
0.25-in. natural draft over the fire, and 200 per cent is secured with a 1-in. 
ashpit pressure. 

Universal Stoker, Fig. 77. Coal is forced into the retort by a steam ram 
bearing a breaker bar. Air is admitted under pressure through tuyeres ar- 
ranged in steps at the sides of the retort. At the rear is placed a supple- 
mental combustion chamber, where the fuel is reduced to ash and dumped 
into the water-sealed ashpit. 







^v V^>^v^Vg;;;5-;; - ^VV"^^?;^:;^^;y^:-':;f:?;t^.i'f ;•;;•:;•/ ■-.^f-yi ^^V ^TI"!"?^^ 



r^ - i: kM 



Fig. 77. Universal Automatic Underfeed Stoker. 



164 



STOKERS 



Wesiinghouse Underfeed Stoker, Fig. 7S, is of the gravity.- underfeed 
t>-pe; the coal is fed to the lower zone, but its movement toward the dump 
plate is aided by the slope of the retorts. Between the retorts are semi- 
circular corrugated tuyeres D, which supplj- air under pressure. The coal is 
moved by the upper ram K, by the lower ram O in the bed of the retort, and 
by the moving "overfeed section"' G at the rear and bottom. The ash dtmips 
are in pairs, pivoted front and rear. Air enters through the tuAeres separat- 
ing the retorts, through the overfeed section, and through box J at the 
front. This stoker is recommended for plants where the load is subject 
to wide and sudden variations. Natural draft can be used at light loads, 
and 400 per cent of rating can be secured for peaks, at 6 to 7-in. pressure 
in the wind box. 




11 i^^y^^^^a 







Fig. 78. Westinghouse Underfeed Stoker. 



Taylor Stoker. Fig. 79. The retorts are sloping, with periorared tuyeres 
in between; each step is V-shaped, the opening being toward the front. The 
coal is pushed into the retorts 1 by feeding rams 5, and is either crowded 
upward or pushed into the fire bj- short-stroke rams 6, 6, the final combus- 
tion taking place on the extension grates 7. The combustible gases are 
ignited in the incandescent zone at the front and top of the coal bed. The 
power dump plate 8 is rapidly oscillated to dislodge and dump the refuse 
and clinkers. In an alternative design the refuse is ground between crush- 
ers, at a speed which keeps the discharge ash-sealed, Bitmninous, semi- 
bituminous, and semi-anthracite, and even lignite coals can be bumei 
At normal ratings a forced draft of 1.5 to 2 in. is used, with 0.03-in. suction. 
A wind box pressure of 3 to 4 in. with 0.03-in. suction, will permit continuous 
operation at 200 to 300 per cent rating. During peaks, from 60 to 80 lb. of 
coal per sq. ft. per hr. can be burned. 



STOKERS 



165 



%y' ^\ ^y. 




Fig. 79. Taylor Underfeed Stoker. 

Riley Stoker, Fig. 80. The retort walls move and also agitate the 
"overfeed grate bars," v^hich supply air for combustion. Farther down the 
slope, at the moving overfeed bars, the unconsumed coke is burned with the 
aid of smaller quantities of air. The refuse finally passes to the rocker 
dump plates, which are in continuous operation ; here the refuse is crushed 
and ejected at a rate depending on the size of the opening. The stoker can 
burn lignite and all grades of bituminous coals. Forced draft is used, up 
to 5 in., with a slight suction. At peak loads 200 to 300 per cent rating 
and over is obtained. 




Fig. 80. Riley Underfeed Stoker. 



166 




L 



^^. 



m^ 



im 



2500 H. P. Installation of Heine Standard Boilers set over Westinghouse 

Underfeed Stokers in the Plant of Harrisons, Inc., 

Philadelphia, Pa. 



STOKERS 



167 



Chain or Traveling Grate Stokers 

IN THE chain grate stoker the coal is deposited on the grate in front, and 
is ignited by the aid of arches. It is then coked, gradually burned to ash 
without agitation or cleaning, and is automatically dumped at the rear. The 
gear-trains driving the pulley-shafts are actuated by a ratchet and pawl, an 
adjustable arm being reciprocated by an eccentric on a line shaft. Chain 
grates handle normal loads efficiently, and with a minimum of smoke, al- 
though the maximum rate of driving is only about 250 per cent. They work 
particularly well with low-grade, free-burning bituminous coals, such as 
those from Illinois and Iowa, containing 30 to 40 per cent volatile and 10 
to 20 per cent ash. With coals of a lower ash-content, the stoker may over- 
heat. 

Continental Chain Grate Stoker consists of small units, with dove-tail 
and semi-circular recesses for locking each grate, and of rollers traveling 
on upper and lower tracks. The ignition arch over the front is made of 
ventilated tile. The depth of fuel bed is regulated by a tile-lined_ gate. 
A water-cooled chamber in front of the bridge wall prevents adhesion of 
clinker. The stoker is built for all grades of free-burning coal and lignite 
with ash content over 7 per cent, and for all sizes from slack to 2-in. nut. A 
suction of 0.2 in. over the fire is sufficient when burning Illinois and Indiana 
coal at a 30-lb. rate, or 0.5 in. at a 50-lb. rate. 




Fig. 81. Green Chain Grate Stoker — Type K. 



168 



STOKERS 



Coxe Traveling Grate. The pressure in the air compartments below 
the tire is varied according to the thicknesses of fuel bed. A combustion 
arch covers the greater part of the grate. This stoker is designed for small 
anthracite and coke breeze, but also operates with free-burning, high-ash 
coals. The former have been burnt at rates up to 50 lb. per sq. ft, per hour. 
Forced draft of 1 to 2 in. is used. 

Type K Green Chain Grate, Fig. 81, emplo^-s a large, flat, ventilated 
ignition arch. In some installations a stationary waterback is placed in the 
bridge wall. Natural draft is used ; about 0.1 in. is required for each 10 
lb. of coal burned per square foot per hour, the usual rate being 30 to 40 
lb- The Type K stoker is designed for free-burning coals. 

Type L Green Chain Grate is built for coking coals. The coal passes 
from the hopper to a stationary inclined plate, where it is coked before 
dropping onto the grate. Either natural or forced draft is used with this 
type, or induced draft when economizers are installed. Installations are 
operated up to 250 per cent of rating. 




Fig. 82. Harrington Chain Grate Stoker. 



Brady (Harrington) Grate, Fig. 82, is designed for forced draft, at 
combustion rates up to 75 lb., although natural draft can be used at normal 
rating. The grate is built of small interlocking bars, giving a continuous 
surface, no parts of which are exposed to excess heat in turning at the 
rear. The air supply at different points is controlled by adjustable dampers 



STOKERS 



169 



Illinois Chain Grate has a slight dip to the rear, and a long, flat com- 
bustion arch. Middle Western coals with over 20 per cent ash are burnt. 
At a 40-lb. rate the draft is 0.63 in. over the fire and 1 in. at the 




i>,''i>_'°'.o;'>.' y',» 'i'rf>^.'^-i'^! VV^io'.^; "o'V'' .'"'>'• ii'?''i':°. ■* 



;oyo'-.'<3. .'o .'o ■/ i .'J^. ■>..','. ^. a' '>lS.-o:6'',:o''^y-i'-.'' riVo 



Fig. 83. Illinois Chain Grate Stoker. 



damper. With coals containing from 10 to 20 per cent ash, 0.4 in. over the 
fire is sufficient. Under forced draft, the draft over the fire can be less 
than 0.15 in., with 1 to 4-in. wind-box pressure. 



170 



STOKERS 



Laclede-Christy Chain Grate, Fig. 84. has a slightly inclined grate, 
in an air-tight setting, with long overhead arch. Air enters through small 
openings in the links, a swinging damper being used to reduce the supply 
at the rear. This stoker is designed for high-volatile, high-ash coals, espe- 
cially those from the West, and operates under natural draft. A chimney 
height of 200 ft. is sufficient for operation at more than 200 per cent rating. 




■' "'^i^ ■■■ *■■' 



Fig 84. Laclede-Christy Chain Grate Stoker. 



Playford Chain Grate. The fiat ignition arch is air-cooled, a water- 
cooled fuel-gate preventing back-firing of coal in the hopper. The bridge 
wall is protected from clinker, and air inleakage prevented, by a fixed water- 
back. In some installations a movable back is cooled by either water or air; 
the material at the back of the grate can then be held back or dumped at will. 
The stoker is adapted for bituminous coals with 25 to 40 per cent volatile 
matter. Natural draft, 0.15 to 0.4 in., is used. 



STOKERS 



171 



National Stoker, Fig. 85. Rows of pushers in recesses in the middle and 
lower parts of the inchned grate are hand operated by levers in the boiler 
front. The fuel is fed, coked and burned as in mechanically operated 
stokers. This stoker is applied to small or medium-sized furnaces- 




Fig. 85. National Hand Operated Overfeed Stoker. 




o 
PQ 

u 
OS 

n 
a 
a 
+j 

Ui 

o 

d 

*C 



0. 
vo 



bfi 
S 

c 
o 

o 
>^ 

o 
o 

u 
PCI 

c 
o 

G 

"a 
6 

0^ 

O 
O 

&/) 



(^ 



173 



CHAPTER 6 



CHIMNEYS AND FLUES 

THE pressure of the draft is the difference in the weight of the column of 
hot gases within the chimney and of the corresponding column of air 
outside. It is measured by the difference in level of water in the legs 
of a "U" tube, of which one leg is connected to the base of the stack and the 
other is open to the atmosphere. The hotter the gases, the higher the 
chimney, or the cooler the atmosphere, the greater is the draft. 

The performance of chimneys is disturbed by many circumstances, 
particularly by the weather. Variations in the barometer affect the draft 
nearly 10 per cent. The draft may be nearly 50 per cent greater when the 
air temperature is zero than when it is 100 degrees. As the quantity of gas 
flowing up the chimney is increased, the pressure necessary to overcome the 
friction of the gas flow is increased, leaving a lower draft reading on the 
"U" gage. 

While there is a minimum height for any draft requirement, the height 
is generally influenced by local considerations. For satisfactory results, 
chimneys should be higher than surrounding buildings, hills, trees or other 
nearby obstructions, so that wind eddies will not interfere with the draft. 

The minimum chimney height necessary in any case depends upon the 
fuel used. Wood requires the least height, good bituminous coal requires 
a medium height, while fine sizes of anthracite need the greatest chimney 
height. The rate of combustion, boiler gas passages, flue design, and the 
number of boilers, also influence the stack height. 

Small plants burning bituminous coal or large anthracite may have stacks 
from 70 to 100 ft. high. If burning anthracite pea or buckwheat, they 
should be 125 to 150 ft. high. Plants of 800 H.P. or more should have stacks 
not less than 150 ft., whatever kind of coal is burned. To burn No. 3 buck- 
wheat at any practical rate, the chimney will have to be more than twice as 
high as would be required to burn pea coal. This height is generally 
prohibitive, and small anthracites are almost invariably burned with artificial 
draft. 

The tallest chimney in the world is the interior stack of the Equitable 
Building, New York, 596 ft. high, serving 3500 H.P. of Heine boilers. 

Chimneys over 200 ft. high are usually unnecessary. Unless conditions 
call for a taller stack, two or more shorter stacks should be erected, as the 
two will usually cost less than the taller stack. There is a diameter corres- 
ponding to the most economical construction for any stack height. Accord- 
ing to W. Deinlein, the smallest product of diameter and height represents 
the chimney of minimum cost. For any given conditions, this relation can 
be established graphically as shown in Fig. 86: Assuming a masonry chim- 
ney, we find from the "H = height" curve that this particular chimney could 
be i75 ft. high by 20 in. diameter, or 125 ft. by 23 in., or 100 ft. by 31 in., and 
so forth. These products are then plotted to form the curve "dH = Relative 
Cost" and we see that the lowest point of this curve occurs at 25 in., for 
which diameter the appropriate height is 115 feet. This is the lowest priced 
chimney that can be built to meet the conditions. 



174 



CHIMNEYS 



3S0 



300 



250 



= 200 



:75 



150 



o 



100 



50 















1 




































1 








M .- 




ck 








_ ^+n„l C-t-^^L. 




: 1 








[ 
























1 




















1 

I 






















^' 


1 

/ i 


















J 


,'-' 




U^ 




\ 












..^i 








X ^^ 










^P^ 


X 






i 
i 
1 


\ 


S 






■---:; 


';y^ 










\ 




v., 


^<^ 

_^«^^«^^ 


^^ 


H- 


= Heigh f 












^>«; 




















1 
























1 




















1 





"I E 3 4 5 6 7 

Chimney Diameter in Feet 

Fig. 86. Relation of Height and Diameter to Minimum Cost of 
Chimney for a given Boiler Capacity. 



The gas temperature in the stack falls as the distance above the entering 
flue increases. This is shown in Fig. 87, based upon tests by Kilhorn and 
Alexander, on a tall masonry chimney. 

An analysis of numerous tests, by E. J. Miller, shows that the observed 
draft intensity usually does not vary more than 3 per cent from that calcu- 
lated when the temperature drop in the chimney is allowed for. Still, in 
general chimney calculations, uniform temperature is assumed, and the 
temperature of the entering gases is the temperature used. Hence, the 
great difference between the draft calculated and that actually observed. 
This difference is stated by different authorities as 10, 15, and 20 per cent, 
and they recommend that appropriate allowance be made. 

In the following treatment, the fall in temperature of the gases as they 
ascend the stack has been taken into consideration. The average temperature 
of the gases in stacks of different diameters and heights has been deduced 
from observation, and curves convenient for general use have been drawn. 

The logical method of treating the subject is to compute the character- 
istics of chimneys, as is done with fans. The minimum draft necessar}- at 
the base of the chimney' should first be found, and then chimney sizes to 
produce that draft at the required capacity can easih' be chosen. In the 
following discussion, reasonable values of air and gas temperatures, and 
operating efficiency, will be assumed and the effect of departures therefrom 
indicated. These assumed conditions must be lived up to in operation, or 
the calculated results will not be attained. 



CHIMNEYS 



175 



240 






T 
















1 




r- 












1 




























220 






1 
































1 




























200 






' 




























































180 








\ 
































\ 


























•160 








\ 
































\ 


























•^140 

Si. 








\ 


























































^ 120 


































































E 

X 100 
o 












V 
































\ 






















80 












\ 


































\ 




















€0 














\ 


































\, 


















40 


















\, 
































V 


\ 














20 






















N 


































N 


X 











































50 








4 


00 








4 


50 








5 


30 



Gas Tempera+ure.degJahr: 

Fig. 87. Fall of Gas Temperature as Distance from 
Entering Flue Increases. 



Chimney Sizes by Horsepower 

T^HE chimney horsepower table of William Kent, modified to include the 
-L draft at the base of the chimney, is given in Table 9. 

The draft to be observed at the base of the stack as given in the table. 
is computed on the following assumptions : 

The horsepower given is the rated horsepower of the boilers. 

The boilers are run at 130 per cent of their rating. 

Five pounds of coal are burned per boiler horsepower hour. 

Each pound of coal produces 20 lb. of flue gases. 

Atmospheric temperature, 60 deg. Barometer, 30 inches. 

Humidity ignored as negligible. 

Temperature of gases entering stack, 500 deg. 

Allowance has been made for the drop of temperature of the gases 
as they ascend the stack. 

As an example, take five boilers, each rated at 160 H.P., making 800 H.P. 
in all. 

From the table, it is seen that this load is met by the following propor- 



tions 



72 inches dia. 100 feet high 0.50 inch draft 
66 inches dia. 150 feet high 0.65 inch draft 
60 inches dia. 200 feet high 0.74 inch draft 



76 



C H I ^I X E Y S 



To decide which of these is appropriate, local conditions must be first 
considered. Then the necessary draft at the stack base must be determined 
from the draft resistances of the fuel bed, boiler setting and so forth, as 
explained later; and the sum of these will determine the draft necessary- at 
the stack base and consequently the minimum height of chimney. Then the 
most economical proportion of height to diameter should be found by apply- 
ing the principle illustrated in Fig. 86, so that the chimne}* of least cost, 
which will meet the various conditions, may be rjdopted. 



Table 9. Chimney Sizes by Horsepower. 



Dia. 
In. 



Area, 

(A) 

Sq. Ft. 



Effec- 
tive 
Area, 
Sq. Ft. 
E = A— 

0.6 Va 



HEIGHT OF CHIMNEY, Ft. 



60 70 80 ' 90 I 100' 110 125 150 175 200 i 225 i 250 



Upper Fig\ire= Commercial Horsepower Rating 

Lower Figure= Draft at Base of Chimney at 130 i>er 

cent of Commercial Horsepower Rating 



Equiv- 
alent 

Square 
Chimney 

In. 
Side of 
Square 

Ve-I-4 



24 3.14 
27 3.98 
30 4.91 



2.08 



3.58 



54 


58 
0.35 

78 
0.35 
100 
0.35 


62 

0.38 
83 

0.38 
107 

0.38 


66 

0.41 

88 

0.42 

113 

0.42 
















■ 


0.31 




















72 

0.31 

92 

0.31 




































* 


119 
















<,, 


0.45 

















22 
24 

27 



33 
36 
39 



5.94 
7.07 
8.30 



4.48 



A 



5.47 
6.57 



115 125 133 141 149 

0.31 0.35 0.38 0.42 0.46 
141 152, 163 173 182 

0.31 0.35 0.39 0.43 0.46 
....I 183| 196 208 219 

....|0.35l 0.391 0.43 0.47 



156 

0.48, 
191 

0.49; 
229 

0.50 



2041 

0.53 
2451 

0.54 1 



268 

0.58 



30 
32 
35 



42 


9.62 


48 


12.57 


54 


15.90 



7.76 
10.44 
13.51 



216 

0.35 



231 

0.39 
311 

0.39 



245 258, 

0.43 0.47| 
330 3481 

0.44 0.481 
427i 449 

0.45 0.49' 



271 
0.51 
365 
0.52 
472 
0.53 



289 


316 


342 


0.55 


0.59 


0.61 


389 


426 


460 


0.56 


0.60 


0.64 


503 551 


595 


0.57 


0.62 


0.67 



492 

0.68 

636 1 675 

0.7l| 0.74 



38 
43 

48 



60 
66 
72 



19.64 
23.76 
28.27 



16.98/ 
20.83; 
25.08; 



536 1 565 

0.45 0.49 
694 1 

0.501 
835| 

0.50' 



593 


632 


0.53 


0.57 


728 


776 


0.53 


0.58 


876 


934 


0.54 


0.59 



692 

0.64 

849 

0.65 

1,023 

0.67 



800, 848 

0.74| 0.77 
981 1,040 
0.761 0.80 
1,105 1,181 1,253 

0.73| 0.781 0.83 



748 
0.70 
918 

0.72 



894 

0.78 
1,097 

0.82 
1,320 

0.851 



54 
59 
64 



78 
84 
90 



33.18 
38.48 
44.18 



29.73^ 
34. 76 J 
40.19, 



1,038 1,107 1,212 1,310 1,400 1,485 1,565 

I 0.54| 0.60| 0.671 0.751 0.80| 0.85| 0.88i 
1,214 1,294 1,418 1,531 1,637 1,736 1,830 



0.55 0.611 0.68 
|1,496 1,639 

0.611 0.69 



0.76) 0.82 0.87| 0.91 
1,770 1,893 2,008 2,116 

0.77| 0.84| 0.89( 0.94 



70 



80 



96 
102 
108 



50.27 
56.75 
63.62 



46.01j 
52.23^ 

58.83 



1,712 1,876 

0.62| 0.70 
1,944 2,130 

0.62| 0.70 
2,090 2,399 

I 0.631 0.71 



2,027 2,167 

0.18| 0.85 
2,300 2,459 

0.79| 0.86 
2,592 2,771 

0.801 0.881 



2,298 
0.91| 

2,609 
0.931 

2,939 
0.951 



2,423 

0.96 
2,750 

0.98 
3,098 

1.00 



86 
91 
96 



114 
120 
132 



70.88 
78.54 
95.03 



65.83' 
73. 22 I 
89.18/ 



2,685 

0.72 
2,986 

0.73 
3,637 

0.74 



2,900 3,100 

0.811 0.901 
3,226 3,448 

0.821 0.91 
3,929 4,200 

0.841 0.931 



3,288 
0.97 

3,657 
0.98 

4,455 
1.00 



3,466 

1.02 
3,855 

1.03 
4,696] 

1.06 



101 
107 
117 



144 
156 
168 



113 . 10 
132 . 73 
153.94 


106.72/ 
125.82 f 
146.51/ 
















4,352, 

0.75 






















































































1 







4,701,5,026 5,331 5,618 128 

0.86 0.95| 1.03| 1.09 . 
5,542 5,925 6,285 6,624 138 

0.881 0.971 1.051 1.12i; 
6,454 6,899 7,318 7,713 ^ 150 

0.89, 0.981 1.071 1.15 



CHIMNEYS 



177 



The assumptions on which the table is based meet all ordinary condi- 
tions. The effect of other conditions will now be discussed and compared. 

As stated above, the draft at the chimney base, as given in the table, 
was computed at 130 per cent of boiler rating. In the example just taken 
the drafts read from the table are those to be expected when the boilers are 
running at 130 per cent of rating or developing 800x130 per cent=1040 B.H.P. 
In the following discussion, the draft read from the table is considered as one 
hundred per cent. 

The first change considered will be that caused by adding or taking off 
boilers, the load on individual boilers remaining the same. Under these 
circumstances, the temperature of the gases entering the chimney remains the 
same, and the draft falls off as the addition of more boilers increases the 
load on the chimney. The rate at which the draft falls off depends upon 
the ratio of diameter to height (H/D) and curves have been drawn for 
different ratios in Fig. 88. These show very clearly that the draft diminishes 
much more rapidly in slender than in squat chimneys. 



(40 

130 

leo 
no 

^100 

<+- 

E90 

"5 80 

I TO 

c^60 

50 

40 

30 

20 













J5 
































a..^ 




!^^^ 


-~J^ 


N 


























2 


^ ^^ 


16^ 


^ 


^^ 


^ 


^ 




























A 






\ 


r^ 


^ 












B 


























N^ 


^ 


)D 




































^ 


v^ 




16 






























^ 


n" 


\; 


































^ 


k 


25] 


'D 
































^ 




































N 


<J5 















































































10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 
Percent of Chimney Ra+ing 



Fig. 88. Percent of Draft Required for Different Ratings of Chimneys 
Based on Boilers Running at 130 Percent of their Rating. 



Taking the first chimney of the above example H/D=100/6=16.7. Using 
the nearest curve given in Fig. 88, where H/D=16, and taking off one boiler 
so that the chimney load is reduced to 80 per cent of chimney rating, the 
draft is now shown (as at C) to be 107 per cent. The draft at 100 per cent 
of chimney rating was 0.50 inch, therefore the draft with only four boilers 
in operation will be 107 per cent of 0.50, or 0.54 inch. 

Continuing with the first chimney of the example, and adding one boiler, 
the load will now be 120 per cent of chimney rating. The draft (as at D) is 
now 92 per cent, so that the draft at the base of the stack with six boilers 
in operation will be 92 per cent of 0.50 or 0.46 inch. 

The change in the draft caused by varying the load on a fixed number of 
boilers will now be considered. The temperature of the gases leaving the 
boilers increases as their rate of driving is increased, as shown by Fig. 90. As 
the temperature rises, the gases become lighter. This increases the static 
draft and lowers the increase of friction loss, as explained later. The rate 



CHIMNEYS 



at which the draft falls off is less than in the previous case, and may even 
rise. The curse is now dependent upon the ratio of square root of diameter 
to height (H \ D) and curses have been drawn for several different ratios in 
Fig. 89. It will be seen that this chart is marked for both chimney rating 
and boiler rating, and that 130 per cent of boiler rating is equal to 100 per 
cent of chimney rating. 

Again taking the first chimney of the example. H \ D^41. Using the 
nearest curse in Fig. 89. where H \ D=:+3. and decreasing the chimnej- load 
to 80 per cent which reduces the boiler load to 104 per cent of rating, the 
draft (as at C) is now 96.5 per cent of that at chimney rating. The draft 
at the base of the stack is now 96.5 per cent of 0.50 or_0.48 inches. At 120 
per cent of chimney rating equal to boilers running at 156 per cent the draft 
i^as at D) is 108 per cent or 0.54 inches. 

rr: 
16: 



k: 





, 


;' 


/ 






Fig. 89. Percent of Draft Required for Different Ratings of 
Chimneys and Boilers. 



On each of the char:s the dotted line A-B represents the proportionate 
amount of draft required. This curse is drawn on the assumption that the 
draft required varies as the square of the horsepower developed in a given 
boiler, which is not true, but is as close as is necessarj-. In Fig. S^, it is a 
horizontal line. The draft required is constant, since the load is varied 
by adding or shutting down boilers. The amount of draft must be increased 
somewhat as more boilers are added, owing to greater length of flues and 
more turns and enlargements. This increase is not large and is different in 
every case, so that it has been ignored in the chart. In Fig. 89, the curs-e 
rises quickh-. In both figures the unnecessary- draft at C is extinguished by 
partly closing the damper, while the defect of draft at D must be made up 
bj- artificial or mechanical draft 

The curses drawn in Figs. 88 and 89 are based on the temperatures of 
the gases leaving the boiler in excess of the temperature due to the steam 
pressure. The curse in Fig. 90. due to Geo. H. Gibson, is based upon the 



CHIMNEYS 



179 



power developed, taken as a percentage of the commercial rating, and assum- 
ing- a steam temperature of 350 deg., or 120 lb. pressure. As Fig. 88 is based 
on the boilers running at 130 per cent of their rating, the constant temperature 
of 500 deg. is assumed as that of the gases entering the stack, while in Fig. 
89 the temperatures appropriate to the power as given in Fig. 90 have been 
used. 




JOO 120 140 160 180 200 
Percent of- Rated Horsepower Developed. 



240 



260 



Fig. 90. 



Excess Temperature of Gases Leaving Steam Boiler as 
Affected by Rate of Driving. 



So far, we have used the same basis as Kent in assuming 5 pounds of 
coal per B.H.P. and 20 pounds of flue gases per pound of coal. These fig- 
ures are sufficiently liberal for reasonably careful operation. But where an 
excess of air is allowed to leak in through defective settings, firedoors, holes 
in the fire, and so forth, the quantity of gases to be dealt with may be greatly 
increased. This increases the load on the chimney. The amount of excess air 

40 

38 

36 

34 
</) 

c30 

_826 
^?4 

£ 



^ 16 













\' 


\ 






































\ 


\ 






































\ 


[\ 








































\l 


\ 






































\ 


\ 


s 






































\ 


\ 






































\ 


K'^ 


\o^ 






































% 




k 






































\ 




\ 






































\ 




\ 


X 




































\ 


> 






^ 


































^ 


^ 












































-^ 



























































































14 



"0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 l9 20 
Coirbon Dioxide (C0^), Per Cent 

Fig. 91. Effect of Excessive Air. Increase in Weight of Gases as CO2 

is Reduced. 



180 




-d 

V 



03 



.3 w 

V 

03 — H 

CO ^ 

o«5 

O 03 
03 fj 

^^ 

o "^ 

03 •> 
U •»-> 

O cS 

G 03 

O u 

(-H "d 

"J s 

O (u 

^^ 



o 2 

+j o 
tuBm 



CHIMNEYS 



181 



isi found from analysis of the flue gases as explained in Chapter 15 on 
BOILER TESTING, and is shown by the percentage of CO2. Fig. 91 is a 
representative example of the weight of gases per pound of fuel with different 
percentages of CO2. With the coal of analysis used in drawing the curve, 20 
pounds of gas per pound of fuel is due to 11 per cent of CO2. If the CO2 is 
reduced to 7 per cent, then the weight of gas is increased to 30 pounds, or 
50 per cent more. Under these conditions a given chimney could only care 
for two-thirds the load expressed in boiler horsepower. In many instances 
overloaded chimneys have been relieved by the addition of forced draft 
and otherwise improved operation so that the weight of gas per boiler horse- 
power has been sufficiently reduced to enable more power to be developed 
without alteration to the chimney. 



Draft and Capacity of Chimneys 

"T^HE curves, Fig. 92, are deduced from observations by Peabody and Miller 
^ and by /. C. Smnllzvood. All are for temperatures above that of the 
atmosphere. Thus, taking gases entering at 500 deg., and atmos- 
pheric temperature of 60 deg., the difference is 440 deg. In a masonry stack 




100 150 200 250 

Height of Chimney, feet 



350 



Fig. 92. Average Temperature of Gases in Percent of Entering 
Temperature according to Height of Chimneys. 

7 ft. diameter, 200 ft. high, the average temperature will be 80 per cent of 
the entering temperature, 440 X 0.80, or 350 -f 60 = 410 deg. as actual 
average temperature. At heavy loads the average temperature will probably 
be a larger proportion of the entering temperature, and at light loads a 
smaller proportion than those shown by the curves. Any such differences 
from the curves given are likely to be negligibly small. 

Fig. 93 gives the weight per cubic foot of the chimney gases under aver- 
age conditions, at different temperatures, and Fig. 94, that of air. 

The static draft appropriate to any chimney can be calculated by means 
of these three charts. Continuing with the last example and taking the 
temperature of the air at 60 deg. (the common assumption in designing chim- 
neys), the weight of air per cubic foot is seen to be 0.0764 pounds. A column 
of air of one square foot cross-section, 200 ft. high, will weigh 200 X 0.0764 
= 15.28 pounds. The column of gas (at 410 deg.) of the same height will 
weigh 200 X 0.484 = 9.68 pounds. The difference, 15.28 — 9.68, or 5.6 lb., 
is the pressure per square foot of the resulting draft. Then the static draft 
is 5.6 X 0.192 = 1.08 in. of water. 



182 



CHIMNEYS 



ao7o 



0.06: 



.if 0.05: 



o. 0.04C 



■n 



0.03C 



aozo 



. _ — »— 

^' I ^ i_ 

'**»^ r>_ , ' ' 

— ^t]' > 

, i_ 



100 200 ;:: -:: ::: e:: ":: soo 9oo looo 

Fig. 93. Weight of Flue Gases, 



0090 



C.085 



Si 



u 
«> 

-SQ075 

c 

3 



0.070 



0.065 



20 40 60 80 

Temperodxirc, Degrees 

Fig. 94. Weight of Air. 



100 



120 



140 



In common practice, the entering temperature of 500 deg. would be taken, 
giving a static draft of 1.26 in,, which is wrong. This static draft of 1.08 in. 
cannot be read on a U-gage. because part of it is lost in overcoming the 
friction of the gases in the chimney. 

The draft loss by chimney and flue friction can be read from Fig. 95. 
The curves are drawn for a temperature of 440 degrees. The draft loss for 
any other temxperature can be obtained by multiplying that read from the 
curves b}' the multipliers given by the upper curve. For instance, take the 
dotted lines as an example ; if the temperature is 575 degrees, enter the upper 
scale with this temperature and proceed vertically downwards to intersection 
with the curve, then horizontally to the right hand scale and read the multi- 
plier as 0.87. If the upper scale be entered with 440 degrees, the multiplier 
is with similar proceedure found to be 1.00. For unlined steel stacks and flues 
multiply the final result by 0.94. 



C H I ]\I N E Y S 



183 



Temperature, Degrees. 



— C\J K3 



oo c iii 



0.70 



"O.50 



1 0.40 



O.30 



§ 0.20 
^ 0.10 





V 


















\ 








! 












\\ 


















\ 


















l\\' 


\ 


















\ 


















\\ 


\ 


















> 


K 






K 


pe 
_ /^ 


i 




l\ ^ 


k 


V 


















\ 








ra fares Multi- 




\\ 


\ 


\ 




















\ 






\/ Draft Loss by 
is Figure-. 


IV 


\ \ 


K\ 


\ 


\ 


















\ 


\, 








\ 


\\ 


\ 


\ 


\, 


^^ 
















\ 


vi 










,v 


v\ 


\ 


\ 


s, 


\J 


,.:] 


<^ 


^/ 


^ 


^ 










\ 







~^r— 


l\ 


\ 


\\ 


\ 




-^^ 


■'a' 










S 


\ 






V 




Ov 




^ 




--i^ 


'^ 





-^ 














"^\. 


\\ 










-^ 





■"■^ 


-^ 


















\\ 


^ 


H 

^ 
r^^ 


^ 


'A^Sec 


ond 







.. , 


■ 





















^ 




^ 


■^E^ 




^ 


i 


=^ 





1 M— 


■ — 











i.6o: 

1.50 
1.40- 
1.30 

1.10- 
1.00' 
0.90- 

0.80 ; 

0.70 
0.60 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 
Area of Circular Chimney or Flue, Square Fee-V. 

Fig. 95. Frictional Draft Loss per 100 Ft. of Circular Flue or Stack (Based 
on 30 Inch Barometer and 440° Gas Temperature). 



The draft loss can be calculated from this formula, due to A. L. 
on which Fig. 95 is based: 

f LV^ 



h 



Menzin, 
(10) 



DT 



/i= Draft loss, inches of water. 
L^ Height of chimney, or length of flue, feet. 
D = Diameter of flue or chimney, feet. 
F = Velocity of gases, feet per second. 
T = Absolute temperature, degrees. 
f — onOR for circular masonry stacks or flues. 
= 0.0075 for unlined circular steel stacks or flues. 
Fig. 95 was drawn with / = 0.008. 
For square stacks or flues having the same area as round ones of 
diameter D, multiply h as found above by 1.06. For other shapes, the follow- 
ing multipliers can be used : 

Ratio of Sides Multiplier 



Itol 
lto2 
lto3 
lto4 
lto5 
lto6 



1.06 
1.09 
1.14 
1.19 
1.23 
1.27 



Taking the last chimney example, 7 ft. diameter by 200 ft. high with an 
average temperature of the gases of 410 deg. and a velocity of 30 ft per 
second we enter Fig. 95 and find the draft loss for 38.5 sq. ft. to be 0.114 
inch. As the curves are drawn for 440 deg. we enter the correction 



184 



C H I :^1 X E Y S 



portion with 410 de^. and find a multiplier of 1.035; applying this to tlie 
0.114 we get 0.118. This is the draft loss per 100 ft., so doubling it we get 
0.24. This result can be checked by the Mensin formula (10). 

Under the assumed conditions the static draft for this chimney is 1.08 
inches. Deducting the friction draft loss of 0.24 in., we find that the avail- 
able draft at the base of the stack is 0.84 inch. This is the "draft" which is 
read on the U-gage. 

To convert this to horsepower, 30 ft. per second multiplied by the chim- 
ney area of 38.5 sq. ft., gives 1155 cu. ft. per second. From Fig. 93 we 
find the weight per cu. ft. of the gases to be 0.484, so that we have 56 lb. of 
gas per second or 201,600 lb. per hour. As we have been assuming 100 lb. 
of gas per hour per horsepower, the rate becomes 2016 horsepower. 

With Western coals, the sizes given in Kent's table should be increased 
25 to 60 per cent. It is wiser, however, to determine the amount of coal 
to be burned per horsepower, either by Fig. 96 or independently of it, bearing 
in mind that the eiTiciency generally attained with poor coal is low, while 
a higher draft loss through the fuel-bed will be read from Fig. 97. 

Chimney proportions of existing stoker-fired plants in different parts of 
the country are given in Table 10. A comparison with the Kent table is 
included. 

Table 10. Chimney Installations in Typical Power Plants. 



COAL-BURNING STOKER-FIRED 


H. P. of 


No. of 
Units 


Chimney 


H/D 


H. P. per 

Sq. Ft. 

of Stack 

Area 


Chimney 
H. P. 

(Kent) 


Percent 

of 
Kent's 
H. P. 


Type of 


Boilers 


Height Diam. 

1 


Stoker 



1,530 

2,500 

2,800 


2 

4 
4 


125 
150 
230 


8 

9 

10 


15.6 
16.7 
23.0 


30 
39 
36 


1,708 
2,400 
3,690 


90 

104 

76 


Taylor 
Roney 
Chain Grate 


3,600 
3,600 
4,000 


6 
6 
8 


225 
225 
210 


13 
11 

12 


17.3 
20.5 

17.5 


27 
37 
35 


6,290 
4,450 
5,140 


57 
81 
78 


Murphy 
Roney 
M urphy 


4,800 
4,800 
5,800 


8 

8 

10 


180 
210 
250 


14 
13 
17 


12.9 
16.2 
14.7 


31 
36 
26 


6,530 

6,080 

11,480 


73 
79 
51 


Chain Grate 
Taylor 
Chain Grate 


9,600 

9,760 

10,400 


16 

8 

20 


275 
250 
300 


16 
19 
18 


17.2 
13.2 
16.7 


48 
34 
41 


11,640 
14,400 
14,100 


82 
68 
74 


Taylor 
Chain Grate 
Roney 


12,000 
15,600 


12 
24 


250 
250 


20 
21 


12.5 
11.9 


38 
45 


16,000 
17,600 j 


75 
89 


Taylor 
Taylor 



Flue Sices. Formula (,10) is appropriate for flues as well as for chimneys. 
As an example, find the draft loss in a straight brick flue 8 ft. high, 4 ft. 
wide, 200 ft. long, with gases at 550 deg., traveling at 30 ft. per second? 
Entering the lower scale of Fig. 95 with 32 square feet and proceeding 
vertically upwards to the curve of velocity of 30 feet per second, and then 
horizontally to the left-hand scale, the draft loss of 0.125 is read. Entering 
the upper scale with a temperature of 550 degrees, and proceeding as directed 
on the previous page, a multiplier of 0.89 is obtained, and apply- 
ing this to 0.125, a draft loss of 0.111 is found. This is for 100 feet, 
so that for 200 feet the loss is 0.222. But this loss is for a circular flue. 
The ratio of sides is 4 : 8 or 1 : 2 for which the multiplier is 1.09, and applying 
this to 0.222, the draft loss for the conditions laid down is found to be 
0.24 inch. 



CHIMNEYS 



185 



Draft Required for Coal 

THE draft required at the base of the chimney is the sum of the draft losses 
caused by the resistance of the fuel-bed, boiler setting, economizer (if 
there is one), flues and dampers, and the draft absorbed in setting the 
gases in motion. 

Fig. 96 will give the number of pounds of coal which will be burned per 
boiler-horsepower-hour. This should be confirmed by the expected evapora- 
tion per pound of fuel, by taking the appropriate point on the evaporation 
curve and then moving vertically to the coal curve, where, for example, an 
evaporation of 10 lb. of water is seen to necessitate burning 3.45 lb. of 
coal per boiler-horsepower per hour. 



12 7 














^'- 


ri 


"^n 






























0^ 


/ 






f^:^ 


















11 6 


\ 










i 


























^ 


\ 






i 














i. 














10 5 




\ 






J' 
















\ 










^ 






\ 


)i 
















6> 




^ 






G O 

5 9t^4 






\ 


4' 
















\ 


x\^o^^ 


y 














<?r. 














.^ 


0^ 


\ 










^ o 








^ 


h^ 


-« 


sFir 


5^ 


rBoj 


Ktfi 






\ 
\ 

\ 












1 
1 






' 


•^^ 














\ 
\ 






7 2 






/ 

/ 
/ 


























■" 


\ 
\ 






> 






























V 


\ 


6 1 


BH 


/ 

lAnir 


10US 






Sem 


iBit 


jmin 


DUS 








Ant 


nrac 


ite 






N 


Low Gro 


de 






Hiqih Qrads; 






Buckwheat 


Barley 
Rice 






n 


High Vo 




■ 














Low Asfi 


I 


High 
.ow |Voloi 


Ash 
tile 





Fig. 96, Quantity of Coal Required for Given Quantity of 
Water Evaporated. 

Knowing the weight of coal to be burned per hour and dividing it by 
the total grate area, the number of pounds to be burned per square foot per 
hour is obtained. Fig. 97 shows the draft required through the fuel-bed. The 
curves have been plotted from a large number of boiler tests and represent 
good general practice. Reference should also be made to Chapter 2 on 
BOILERS. 

The draft loss through a regular Heine Boiler setting is given by Fig. 98, 
for both one and two passes. With poor management, allowing excess 
air, the draft required will be greater. Fig. 98 is based on the use of 12 
cu. ft. of air per horsepower per minute. It can also be used to show 
the increase of draft necessitated by an increase of air due to poor firing 
or leaks. Suppose that 15 cu. ft. of air per horsepower per minute is used 
instead of 12. Then the air used is 15/12 or 125 per cent of that forming 
the basis of the chart. The actual proportion of rated horsepower developed 
is multiplied by 125 per cent to find the draft necessary. If the boilers are 
running at 120 per cent of rating, 120 X 125 = 150 per cent, and the draft 
required is read for a single pass boiler as 0.28 inch. 

For cross or vertically baffled boilers, a sufficiently close approximation 
is obtained by adding 10 to 20 per cent to the draft loss read from Fig. 98. 



186 



CHIMNEYS 













/ // / 


P90 




. ,,//// / 


i 1 i i 


IN//// / 


a - 








/ 


i /X / / 1 




t 1 t 




/ 




//f/ / y 


c 


■ r ; 








//> / / ^y 


ei 




■'/ 


■% 


/ 


/ / / y^ y" 


- 




'■"'/ 


^ 


/ 


■'V / y^.-y^ 


s 




-/ -f 




-/ 


y .y^y^ yp^ 




_ 


.t// X 


/ 
^ 


y 


3^- y^^y^ y^y^y^ 


z" 


\ 1 / 


^ -"y^l^-'J-^^^^^^^ ^-^^ 


-' ' 


• /> 


y y 




y 


Jy^^^^yt^t:^^^'^'^ 




'yy 




^^ 


^ 


i^it^glX^^^'^ 




^<>^ 








' 















2 "^ 
Fig. 97 



7c 4-0 



Draft Required Through Fuel Bed for 
Different Grades of Coal. 







Fig. 98. Draft Loss Through a Regular Heine Boiler Setting, 
Compared for One and Two Passes. 

The draft loss through economizers 5 to S ft wide can var>- between 
0.02 and 0.5 in. for each 10 ft. of length. They are generally built long 
and narrow with tubes 9 to 12 ft. high, because their efficiency is greater 
as the speed of the gases is increased, as is shown in discussing heat transfer 
in Chapter 11. The draft loss can be computed from 



CHIMNEYS 187 



h= (^-^0^) ll^NT (11) 

10" ^ ^ 

/i== Draft loss, inches of water 
W = Weight of gases, pounds per hour, divided by the number 

of lineal feet of pipe in each economizer section. 
i\r = number of economizer sections. 
T =: mean absolute temperature of gases, degrees. 
The draft loss through breechings and flues can be taken as 0.1 in. of 
water per 100 ft. length and 0.05 in. for each right angle turn, if the area 
is about 20 per cent greater than that of the stack. 

The loss due to altering the speed of the gases at each abrupt enlargement 
and change of shape is : 

/j= Draft loss, inches of water. 
Vi and F2=: Different velocities, feet per second. 

r= Absolute temperature of gases, degrees 

In long flues having several sudden enlargements, changes in form of cross- 
section and sharp turns, the loss may be considerable. 

The draft lost in accelerating the gases is: 

h = 0.125 J— 
T 

For a gas temperature of 500 deg., this becomes 

7680 

The following are values of draft lost in producing velocity for practical 
conditions : 

Velocity, feet per second 20 30 40 50 60 

Draft loss, inches of water 0.05 0.12 0.21 0.33 0.47 

The foregoing draft losses should be tabulated for any given case, 
showing the assumptions on which they are based, as in the following 
example : 

Fuel-Bed Resistance 

Boilers, 200 H.P. Grate area, 40 sq. ft. Good bituminous run of mine 
coal. Say 3.75 lb. of coal per hour per horsepower, as in Fig. 96. 
Boilers to operate at rated capacity 200 X 3.75 := 750 lb. of coal per 
hour per boiler. Divide by 40 sq. ft. of grate = 19 lb. per sq. ft. 
per hour. Read from Fig. 97 0.21 

Boiler Resistance 

If single-pass Heine boilers, read from Fig. 98 as 0.12. If desired, 
allow 20 per cent for more air, reading draft at 120 instead of 
100 per cent 0.18 

Breechings and Flues 

Flue 80 ft. long at 0.10 per 100 ft. gives 0.08 and two bends at 0.05 
each, 0.10. Tapers where required, no abrupt enlargements 0.18 

Velocity of Gases 

Say 25 ft. per second so that - gives 0.08 

Minimum draft at chimney base necessary to operate the plant 0.65 




St. Joseph Lead Co., Rivermines, Mo., operating 7000 H. P. of 
Heine Standard Boilers. 



CHIMNEYS 189 

Chimney Sizes as Determined by Gas 

IN departing from ordinary conditions, for which Kent's table was de- 
signed, it is well to make calculations on the basis of the quantity of gas 
to be dealt with, rather than on weight of fuel or horsepower. The 
quantity of gas can be based on the heat value of the coal, as recom- 
mended by V. J. Azhe. It has been shown that the weight of air required 
per 10,000 B. t. u. generated, varies with the available hydrogen in the fuel 
from 7.65 lb. for anthracite to 7.04 for oil. In solid fuel the maximum varia- 
tion from 7.6 is less than i 1 per cent. Therefore, while the weight of air 
per pound of coal will vary greatly with its heat value, the weight of air 
per horsepower for 100 per cent boiler and furnace efficiency will remain 
constant at 25.4 lb., and the weight of flue gases at about 31 pounds. Dividing 
this by the efficiency, we have the weight of gas per hour per horsepower 
developed. Following are the weights of gases for different fuels : 

Efificiency, Weight of Gases, 

percent lb. per hr. per H. P. 

Anthracite ; 65 48 

Semi-Bituminous 60 52 

High grade Bituminous 55 56 

Illinois Bituminous, poor 50 62 

Oil 70 42 

The volume of the gases at any temperature is obtained by dividing the 
total weight by the weight per cubic foot as read from Fig. 93. Dividing this 
volume by 3600 times the chimney or flue area, will give the velocity in 
feet per second. 

The following have been recommended as economical velocities, consid- 
ering the total quantity of gases : 

Velocity, 
Gases, lb. per hr. feet per second 

1,700 10 

8,300 15 

25,000 20 

83,000 25 

200,000 30 

415,000 35 

830,000 40 

1,330,000 45 

These velocities should be considered only as approximate. The draft 
losses should be determined for several velocities with different sizes of 
chimney so that the most economical can be chosen. 

Chimneys for Oil, Gas and Wood 

GENERALLY the sizes of chimneys calculated on a gas basis are much 
smaller than those found from Kent's table. Ample allowance should 
be made for driving boilers above their rated power, poor coal, poor firing, 
leakage of air through brickwork and from idle boilers. 

With oil burning excessive draft is more wasteful and more likely to 
occur than with coal. Undue chimney height and capacity must therefore 
be avoided. The loss of draft through the burners, boiler setting and flues 
is considerably lower than for coal, because the weight of gases per horse- 
power is less ; the weight per pound of fuel is greater, however, as 
shown in Fig. 91. The temperature of the gases is lower, so that oil- 
stacks produce less draft than coal stacks. The burners, however, give some- 
what of a forced draft effect. Defective draft is also to be avoided, since 
pressure within the boiler setting generally causes rapid deterioration of 
brickwork. Owing to the smaller quantity of gases, the chimney diameter 
should be smaller. 



190 



C H I ^1 N E Y S 



C. R. Weymouth observes that the necessary height for oil chimneys is 
much less than ordinarily supposed when boilers are operated at rating, and 
considerably greater at heavy overloads. 

The sizes of oil chimneys should be based on the maximum load and 
the draft resistance due thereto, rather than on the rated horsepower of the 
connected boilers. Table 11 is based on the horsepower developed (not on 
rated horsepower of boilers, as was Table 9 for coal) when the boilers are 
being operated at 150 per cent of rating. It is a modification of C. R. Wey- 
mouth's table for plants at sea-level, assuming temperature of air as 80 
deg. and of gases as 500 deg. With properly designed connections and short 
flues, the sizes given will be found satisfactory. 

Table 11. Chimney Sizes for Oil-Burning Plants. 





HEIGHT ABOVE FLOOR LINE, FEET 


Dia. 
In. 


80 


90 


100 


110 120 130 


140 


150 


160 


30 
33 
36 


206 
356 
312 


249 
310 
379 


280 
349 

427 


304 
381 
466 


324 
405 

497 


340 
426 
523 


354 
444 
545 


366 

459. 

564 


377 

472 
581 


39 
42 

45 


376 
443 
518 


455 
539 
630 


514 
609 
713 


561 
665 

779 


599 
711 
834 


631 
749 
879 


657 

782 
918 


681 
810 
952 


701 
835 
981 


48 
54 
60 


599 
779 
985 


729 

951 

1.200 


827 
1,080 
1,370 


904 
1,180 
1,500 


967 
1,270 
1,610 


1.020 
1,340 
1,710 


1,070 
1,400 
1,790 


1,110 
1,460 
1,860 


1,140 
1,500 
1,920 


66 

72 
78 


1,220 
1,470 
1,750 


1,490 
1.810 
2,150 


1,700 
2.060 
2,460 


1,860 
2,260 
2,710 


2,000 
2,430 
2,910 


2,120 
2,580 
3,090 


2,220 
2,710 
3,250 


2,310 
2,820 
3.380 


2,390 
2,910 
3,500 


84 
90 
96 


2,060 
2,390 
2.750 


2,530 
2.950 
3,390 


2,900 
3,370 
3,880 


3,190 
3,720 
4.290 


3,440 
4,010 
4.630 


3,650 
4,260 
4,920 


3,840 
4,480 
5,180 


4,000 
4,670 
5,400 


4,150 
4,850 
5,610 


102 
108 


3,140 3,870 1 4,440 
3,550 4,380 | 5,020 


4,900 
5,550 


5,290 
6,000 


5,630 
6,390 


5,930 
6,730 


6.190 
7.030 


6,430 
7,300 


114 
120 


3,990 
4,440 


4,920 
5,490 


5,650 
6,310 


6,250 
6,990 


6.760 
7,560 


7,200 
8,060 


7,590 
8,490 


7,930 
8,890 


8,250 
9,240 



Analysis of figures on several oil chimneys shows the height to be be- 
tween 100 and 180 ft.; the diametjer 1/10 to 1/15 of the height, depending 
upon local conditions ; one square foot of chimney area serves 40 to 50 rated 
horsepower of boilers. 

The general practice of engineers on the Pacific Coast, states George 
Dorward, is to use 50 per cent of the area as stated in Kent's table for stacks 
for coal. For Heine boilers up to 200 H.P., stacks not in excess of 60 ft. in 
height from the boiler room floor line to the top of stack, are the general 
practice. Over 200 H.P. the same rule is used, i. e., 50 per cent of the area 
as stated by Kent, and not in excess of 80 ft. in height. This practice, it 
has been found, works very successfully. 

With blast furnace gas, the volume of chimney gases is greater and at 
a higher temperature than with coal, so that stack diameters are about the 
same. The draft loss through horizontally baffled boilers runs from 0.6 to 0.9 
in. when operating at capacities up to about 175 per cent of rating, which are 
attained in practice with chimneys from 115 to 140 ft. high. 

As in oil-burning chimneys the height and capacity should be deter- 
mined by the draft requirement at maximum capacity. Excessive and defec- 
tive draft should be avoided as causing waste and setting deterioration 
re5pectivel3\ 



CHIMNEYS 



191 



When burning zvood, economy of operation is not easily realized ; large 
quantities of excess air and high stack temperatures are not uncommon. 
Compared with coal burners, wood burning chimneys can be much lower. 
Owing to the greater volume of gases, the diameter should be 10 per cent 
greater than for coal. 

Because of the variations in the properties of different kinds of wood, 
variations in size and wetness, and different methods of firing, draft losses 
through the fuel-bed and boiler setting can be approximated only. 

Wood burning chimneys are best located directly on top of the boiler, to 
avoid accumulations of unburned particles that might otherwise be deposited 
in the base of the stack. Such deposits have been ignited, thus destroying 
the stacks. If such accumulations cannot be avoided, the lower part of the 
stack should be lined with firebrick. 

Municipal refuse destructors and garbage incinerators should have chim- 
neys at least 200 ft. high to meet popular demand that the effects of odors 
be eliminated. High-temperature destructors operated under forced draft do 
not require such heights to take care of the draft; and with proper handling, 
no objectionable odors are emitted. 

Owing to variation in the proportion of combustible matter and water in 
the refuse of dift'erent cities, and the frequent use of coal or oil when only 
the garbage is burned, no general figures on draft requirements are possible. 
For any particular city, these proportions are usually known or ascertained 
sufficiently closely so that boiler and chimney sizes can be determined. Un- 
sorted municipal refuse as collected averages one-third carbon, one-third ash, 
and one-third water. Boilers and chimneys based on this proportion will give 
satisfactory results. 

Evasc or Venturi Chimneys are used to a limited extent in Europe and 
a few have been installed in this country. Fig. 99 is diagrammatic and 
explains the system, which is identical with that of jet-blowers and ex- 
hausters. 



-ivase Chim/t9if 




Fig. 99. Evase Chimney. 



192 



CHIMNEYS 



A fan supplies air for the motor jet, which creates a greater vacuum at 
the chimney base than the vacuum due to the natural draft of the chimney. 
Roughly speaking, the ratio between the vacuum at the chimney base and 
the air pressure at the motor jet equals the ratio between the area of the 
air nozzle and the area of the throat of the chimney. This ratio may be 
conveniently made from 1 : 6 to 1 : 10. 

Usually each stack is connected to one or two boilers. Therefore, since 
the throat diameter is kept small, such stacks may be made only 50 to 75 
feet high without disturbing the proper proportions. 

With the low stack height and small throat diameter, only light loads 
are carried on natural draft, and the motor jet is used for the higher ratings. 
The draft may be controlled either by varying the area of the motor nozzle, 
or by var\ang the air pressure with a damper in the air pipe, or by using a 
variable speed motor to drive the fan. 

Chimneys at Altitudes 

AT high altitudes the specific gravity of the gases is B/30 of the specific 
gravity at sea level, where B is height of barometer in inches due to 
altitude, which may be read from Fig. 100; therefore their velocity through 
the fuel-bed, boiler setting and economizer must be increased by 30/5 in 
order to deal with the same weight of gases. Since the draft loss varies as the 
square of the velocity and as the specific gravity of the gases, it will be 30/5 
or R times the draft loss at sea-level. This ratio is given in one of the 
curves of Fig. 100 or can be calculated. 



30 60 
29 

?8 50 
27 

26 40 
25 

24 30 
23 
22 
21 f* 


^ 


^ 














1 ! 


























N 


^~" 




^, 


-^ecrr, . 




























\ 


\ 


^ 






^^ 


f^ 


v^ 
















/ 












X 


<^ 


^f 



















A 


/ 


















"^ 


^ 


P^c 














/^ 


r~ 


~-^ 























"^ 


^^ 


■^ 








y 


/ 






^^ 


























"^ 


U 


by* 






^ 


^ 


y 
























(\ 




p.. 




^ 




^ 






























e . 


^ 


^ 




^, 


^^ 




2 3 


















-tfS 


'^.^■^^^ 














■^ 


















f^ 


^ 








e^sl 


^^ 


d 


-^ 
















f. 


^ 




^ 






jt^lE 


.+«:] 


A 


eoij; 










u 










^ 


^ 


^ 




fc^l 


\jr^ 


^ 
























^ 


^ 


r^ 




























o 

GO 


^ 


^ 


^ 





































1000 



^ooo 



5000 



4000 5000 6000 

Altitude, Feet 



7000 



1.7 



1.5 



1.2 



8000 9000 \0000 



Fig. 100. Factors to be Used in Calculating Draft Losses in 
Chimneys at High Altitudes. 

The draft lost in giving velocity to the gases and at sudden enlarge- 
ments is 5/30 of that lost in giving the same velocity at sea-level. 

For the same draft loss with the same length of flues, their diameter 
(or equivalent diameter) must be increased i?°**. But it will simplify mat- 



CHIMNEYS 193 



ters to make this increase the same as the increase of chimney diameter, 
the flue area continuing to be 20 per cent greater than that of the chimney. 
The draft loss through the flues will then be a little less than at sea-level. 

The draft power of the chimney is primarily 5/30 of that at sea-level. 
But the normal temperature, being less than at sea-level, reduces this ratio. 
The height necessary to give the same draft at the base would have to be 
increased as 30/5, nearly. But the increased height is accompanied by a 
lower average temperature within the chimney and by an increased friction 
loss due to the increased height. Also, the draft required at the chimney base 
is increased as 30/5 less the advantage derived from the larger flues men- 
tioned above. If the diameter of the chimney is not changed, the velocity is 
greater with still more friction loss. 

From a careful analysis of these changes, compared with results in actual 
practice, it is recommended that the height be increased as (/?i-3), and the 
diameter as (7?"-"). Curves are drawn in Fig. 100, giving both of these ratios. 

Take the example set forth in tabular form on page 187, resulting in a 
chimney say 150 ft. by 66 in. diameter at sea-level, and assume that the plant 
is to be at an altitude of 5000 feet. From Fig. 100, read R"-^ as 1.28 and 
150 X 1.28 equals 192 feet. Read i?o.6 as 1.12 and 66 X 1.12 = 74 in. 
diameter. 

The figures for any given design should be checked as follows : A table 
like that on page 187 should be prepared, showing the draft necessary at the 
stack base, the barometer ratio R being considered. The static draft of the 
stack of the sizes derived as in the last paragraph should be calculated, 
taking the gas temperature average from Fig. 92. The weight of air and gas 
taken from Figs. 93 and 94 are divided by R from Fig. 100 and their dififer- 
ence, multiplied by the height of the stack and by 0.192, is the static draft in 
inches of water. The friction loss is now read from Fig. 95 or calculated 
from the formula (10) and corrected by dividing by R. It is then deducted 
from the static draft, giving the available draft at the base of the stack, 
which can be compared with that required. 

As the altitude is increased, the height of the chimney increases fasteir 
than its diameter ; consequently the proportion of diameter to height will 
sometimes become unmanageable. This can be overcome by increasing the 
grate area or by the use of induced or forced draft. 



Chimney Construction 

CHIMNEYS for modern power houses and industrial plants are made of 
steel plate, radial brick or reinforced concrete, either lined or unlined, 
and are usually of circular cross section. For the same area a round chimney 
has a greater capacity ; its shape requires the least weight for stability, and 
presents the least resistance to the wind. A maximum wind velocity of 100 
m. p. h. is used in the design of such stacks, the equivalent pressure being 
taken at 50 lb. per sq. ft. for flat surfaces, and 30 lb. per sq. ft. of projected 
area of circular stacks. 

The following notes deal only with the practical features that must be 
considered in selecting the type of stacks. The structural design of a chim- 
ney, including calculations for foundation, stability and strength, is an intri- 
cate subject, which is a study for the chimney specialist. 

Chimney foundations are usually made of concrete in a mixture of 1 part 
cement, 2^ parts sand, and 5 parts broken stone or gravel, and poured in a 
'"wet" condition in layers 6 to 8 in. thick, which are thoroughly rammed into 
place. The safe bearing load for ordinary soil is 2 tons per square foot, 
because the chimney represents a concentrated weight on a small area. This 
is considerably lower than the loads permissible in building construction. 



194 



CHIMNEYS 



Foundations for brick chimneys are not as massive as the foundations 
used for steel and reinforced concrete stacks, because they function only as 
supports of the chimney column. In steel and concrete construction the 
foundation acts both as a support and anchor for the stack, the two forming 
practically one mass, giving the desired stabilit}". Reinforcing bars are 
frequently used. 

Table 12 indicates the proportions of foundations necessary for self-sup- 
porting steel and radial block stacks. The least depth and width of square 
or block foundations are considered. In steel stacks with a foundation hav- 
ing tapering sides, the widths at the top should not be reduced more than 3 
or 4 ft. over those given in the table. For normal soil, the foundations sup- 
porting brick stacks can be battered or stepped off. using the widths given 
as the size of the bottom slab. The top slab should be at least a foot wider 
than the stack, all around, and the offsets made so that a line drawn along 
the edge of foundation will make an angle of 60 deg. with its base. 

Table 12. Dimensions of Concrete Foundations For Brick and Steel Stacks 



Stack 



Radial Brick 



Self-Supporting Steel 



Diameter, Feet Height, Feet Width, Feet Depth, Feet Width, Feet Depth, Feet 



100 

125 
150 



12 

16; 

20 



'>2 



4M 
5 

6 



16 
20 
23 



1 


175 


241. 


- 


26 


8,4 


8 


200 


29 


8 


29 


9H 


9 


200 


30 


8 


31 


10 


10 


200 


31 


9 


32 


lOH 



In poor soil, it may be necessan.- to sink piles. These are usually spaced 
2 to 2y2 ft. on centers, and the tops cut off below the surface water line. A 
bed of concrete 2 or 3 ft. thick, into which the piles extend, is then formed 
as a base to receive the regular chimney foundation. 



Self- Supporting Steel Stacks 

SELF-SUSTAINING stacks as a rule are practically straight; that is, the 
walls above the flue openings are parallel. The base section can also be cyl- 
indrical. However, it is usually flared and includes the flue connection. The 
height of the bell-mouth base depends, therefore, upon the run of breeching 
and the location of the flue opening. \Vhen the flared part is one-quarter of 
the stack height, the sides take the slope of a cone having its apex on the 
center line along the top of the stack. This flared base has a diameter about 
one-third greater than the stack proper, permitting the connection of a larger 
flue, and the entr}- of the flue gases with the least interference. 

The flue opening in the plate of the chimney base weakens the structure, 

and requires reinforcing. Stiffening members across the top and bottom of 
the opening are sometimes used. More often the cut-away section is strength- 
ened by angle or T-shapes riveted to the sides and extended beyond the top 
and bottom of the opening, or a combination of these methods can be used 
to reinforce the flue opening all around. 

The flanged base plate riveted to the bottom of the base section is gen- 
eralh' made of two or more cast iron segments. More modern practice calls 
for a built-up steel base ring. Equally spaced around this are lugs drilled for 
the anchor bolts that hold the stack down to its foundation. 



CHIMNEYS 195 



Above the base the stack is divided into several sections, each consist- 
ing of from five to twelve courses, 4 to 7 ft. high. Each course is made up 
of one or more sheets, depending upon the stack diameter. Lap joints are 
invariably used for vertical seams and often for girth seams ; the latter are 
also made with butt joints either inside or outside of the shell. Fre- 
quently intermediate courses have lap joints, but the sections are assembled 
with butt joints that reinforce the stack. In unlined stacks, an outside butt 
joint is preferred as it leaves the stack smooth on the inside. In lined stacks, 
the inside connections can be utilized to support the brickwork. Butt joints 
can be made either with the ordinary straps, or else flanged with angles 
riveted to the shell and bolted together. The riveting is generally figured on 
a factor of safety of four as a minimum. 

It is a moot question whether self-supporting steel stacks should be 
lined. The brick lining does not add to the strength of the chimney, although 
often the stack must carry it. Sometimes the lining is isolated and made 
self-supporting, acting as an inner core. Moisture may collect in the air 
space formed between the Hning and the shell, thus promoting corrosion. 
The lining reduces radiation and protects the steel from the corrosive action 
of the chimney gases. 

When a lining is used in a steel stack it should be carried up the full 
height. Radial firebrick, common brick, concrete and sometimes a filler of 
sand for the air space provided by independent linings are used for lining 
construction. Generally a 4-in. wall supported by an angle iron ring fastened 
to the stack every 15 to 20 ft. will serve. The lower section of stack can be 
lined with firebrick, and the upper section with common brick, using fire clay 
and cement mortar joints respectively. For an independent lining 8-in. brick 
will be required for the lower half of the stack and 4-in. brick for the upper 
half. The brick can be set close to the shell, or an air space of 1 to 2 in. left 
between the steel and the brickwork. 

To preserve the stack, the steel is usually given one coat of paint on 
both surfaces before erection. After the stack is in place, it is usually treated 
with two or three coats of heat-resisting paint. This is intended to protect 
the stack from the corrosive action of the atmosphere as well as to prevent 
air inleakage. 

To maintain the stack a painter's ring should be fitted near the top. This 
consists of a circular metal track with trolley and block to facilitate painting. 
In the base of the stack a cleanout door should be provided for access to 
the interior and for the removal of soot and cinder accumulation. Standard 
size cleanouts measure 24 1)y 36 in. and are made of either heavy cast iron 
or steel plate fitted with frames, hinges and clamps. The contact surfaces 
should be planed so that the door will be air-tight when closed. It is also 
advisable to install a steel ladder extending from the base to the top of 
the stack. This can be on the inside, although it is generally placed on the 
outside about 8 in. from the stack and fastened to the shell through riveted 
bracket connections. Ladders are frequently built with 3-in. side bars, ^ in. 
thick, with rungs or steps of ^-in. round iron, 15 to 18 in. long, and spaced 
12 to 15 in. on centers. In fastening the ladder to the stack, care must be 
taken to prevent strains due to the unequal expansion and contraction of the 
steel shell and the ladder. 

Table 13 illustrates the size and sections and thickness of plate used in 
the construction of self-supporting stacks. Other instances of good practice 
are afforded by the stacks serving some of the large central stations. 

Four steel stacks in an electric light plant, each 297 ft. above the boiler 
grates and 21 ft. in diameter, are made of }i-m. and ^-in. steel plate in 
courses 7 ft. high. Ten vertical stiffening posts of 6 by 4 in. angle iron are 
riveted to the inside of each shell. At each 20 ft. of height two angle irons 
support a stack lining, which consists of 1-in. concrete and 4-in. red brick 
for the entire height. An 18-in. steel ladder on the outside gives access to 



196 




CHIMNEYS 



197 



Table 13. Plate Dimensions For Self- Supporting Steel Stacks 



Diameter, 
Inches 


Total 
Height, 

Feet 


Bottom 

Section, 

Including 

Flare 


2nd 
Section 


3rd 
Section 


4th 
Section 


5th 
Section 




Height 

Feet 


Plate 
Inches 


Height 

Feet 


Plate 
Inches 


Height 

Feet 


Plate 
Inches 


Height 
Feet 


Plate 
Inches 


Height 

Feet 


Plate 
Inches 


54 


100 
165 
185 


40 
30 
65 


5 

16 


30 
50 
60 


H 

5 

16 
5 
16 


30 
45 
60 


3 
16 

M 
}4 










66 


40 


3 
16 






78 
















120 


200 
225 
250 


50 
85 
80 


H 

JL. 
16 

'A 


60 
20 
30 


5 
16 

Vs 

7 
16 


90 
25 
30 


5 
16 

H 








132 


95 1^ 






144 


30 


5 
16 


80 


14 



each stack, and a gallery or grated walkway with hand railing is placetl 
around the top. The stacks rest on plate girders that are part of the build- 
ing construction, and are also braced against swaying and wind action. 

In a street railway plant the two steel stacks, each serving 16 boilers, 
are supported and braced by the framing of the building. The stacks are 132 
ft. in height above the foundation and are made in three sections of 5^-in., 
>2-in. and ^-in. steel plate, each 44 ft. high. An 8-in. red brick lining, backed 
by 1-in. cement, is supported every 25 ft. on rings that stiffen the stacks. 

Another central station has three stacks, each 260 ft. high and 22 ft. 
diameter. The support and wind bracing is furnished by the building con- 
struction. Five sections varying in thickness from ^/ic to ^-in. plate make 
up the height. At each section an angle iron stififener and Z-bar ring support 
the lining, which is of 4-in. red brick backed with 1 in. of concrete. 

The details of a self-supporting steel stack for moderate size plants are 
shown in Fig. 101. This stack, which was designed and fabricated by the 
Chicago Bridge & Iron Works, is 13 ft. diameter and 185 ft. high. It is made 
up of 32 courses in five sections, including the base with the flue opening. 
Each course consists of three sheets and is about 5 ft. 9 in. high. The thick- 
ness of plate varies from ^-in. at the top to 3/^-in. at the bottom. The stack 
is anchored to a concrete foundation on top of which is a sectional cast iron 
base 2 in. thick, in 12 segments. Immediately above the base ring and 
riveted to the base of the stack are 24 built-up steel plate lugs that hold 
the anchor bolts. 

The base section is conical or tapered, 18 ft. high and 19 ft. diameter. 
The first parallel or cylindrical plate course above this is 13 ft. 1]4 in. while 
the last course at the top is only 1 in. less inside diameter. The individual 
courses 7 ft. high. Ten vertical stiffening posts of 6 by 4 in. angle iron are 
the different girth seams. In the base section a flue opening 7 by 20 ft. is rein- 
forced by plates and angles to strengthen the cut-away part of the stack. A 
steel ladder on the outside extends the full height. It is 14 in. wide with side 
bars 2 by }i in., and rungs of S/^ in. square iron. The ladder is strapped 
to the shell at the top of every second course, 8 in. from the stack. 



Guyed Steel Stacks 

nn HE guyed or supported steel stack is designed to simply carry its own 
^ weight. Stability or resistance against wind pressure is cared for by fas- 
tenings to adjoining walls or by guy wires. Guyed or supported stacks do not 
require heavy foundations, because they are much lighter than self-supporting 
stacks. Usually they are riveted to the smoke breeching or else arc con- 
nected with the smoke up-take and with the boiler setting. 



198 



CHIMNEYS 



JW/^^'Z- 



2-Bars2''xWx-- 
IS'-Tk" \ 



I 



?-BenfBars 
7V/8'xO-llii'- 



W^ 



■V- 



m 



•iS'W Radius 
't Plate Top 






V^ 



<-/" 



.'Splice 

<-6-6'WI?adius 
i. Plate Boft 



■'A" Plate 
WP/vets 



I 



PART OF TOP SECTION 




^i^ 



\<-9-6WPactia5 
i Plate 



Sottom of dBase 



PART OF BASE SEaiON 



Bent Plate 
IO"xWW'-8W- 

Bent Plate , 
lOW'xWW-sA 



Bottom X 
of Plate-'' 




DETAIL OF ANCHOR 
BRACKH 




TxIO'Flue— 
Opening 

l2"xW- 

l2"x'/2" 
4"x&'x%"L--\ 

12 "xW-- 



k 19'-0--^ 

WlO-yClBase-^ 



Fig. 101. Construction Details of a Self- Supporting Steel Stack. 



CHIMNEYS 



199 



The thickness of plate used varies considerably and is largely governed 
by the degree of permanence required. Corrosive action by the elements and 
stack gases gradually reduce the thickness of the sheets until the stack is no 
longer safe. 

The thickness of plate is ordinarily kept within the limits given in 
Table 14. 

Table 14. Dimensions of Guyed Steel Stacks. 



Diameter 


Thickness of Plate 


Inches 


Maximum 


Minimum 


30 
36 
42 


No. 8 gage 

Vi6 in. 

yk in. 


No. 10 gage 
No. 10 gage 
No. 10 gage 


48 
54 
60 


Va in. 
Vio in. 
Vi6 in. 


No. 8 gage 
Via in. 
Vie in. 



The size of rivets used should be : 

y% in. diameter for No. 10 and No. 8 gage plate. 

Vi6 in. diameter for Vie in. plate. 

'/le or y2 in. diameter for ^ in. plate. 

Yz or Y^ in. diameter for Vie in. plate. 

The circumferential pitch is generally made equivalent to one rivet for 
each inch of diameter of the stack or 3^/7 in. pitch, and the longitudinal 
pitch is made 3 to 4 inches. 







Fig. 102. 



b c cl 

Styles of Joints for Guyed or Supported Steel Stacks. 



200 



C H I ]\I N E Y S 



Tt is common to make the plates thinner in the upper portion of the 
stack. As the corrosive action is more energetic at the top, many prefer 
to make the upper part thicker than the lower, or at least to keep the 
thickness the same for the full height. 

The plate courses may be assembled as shown in Fig. 102, in which 
the "shingle"' lap (a) is composed of tapered sections and is designed 
to shed water. In joints like (b) the larger sections slip over the ends of the 
smaller sections and all the sections are parallel or cylindrical.. With another 
method (c) the lower end of the upper course slips into the lower course. 
Sometimes a strap-joint (d) is used, in which the ends of sections are butted 
together and a steel band placed around the joint and riveted to each plate, 
making a very strong but much more expensive chimney. 



■^ '> 5" Band, inside and outside 



J^-^ 



<-72"l.D.'-> 



t.^ — mm 



Note W Rivets to be 
driven hot and tight 
On vertical seams 2'/2" 
centers, on girth seams 
2"centers. 



lS/i6"Diam. 
Drilled Hole 



^''/4"Steel Plafe 



Gvy Lugs 
and Strap 



If 



03 




Details of &uy Strgip 
■ Rivet to Breeching 

Fig. 103. Construction of a Guyed Steel Stack. 



C H I IVI N E Y S 201 



While each of these methods have their advocates, the best practice ap- 
pears to be indicated by (c). With (a) the seams cannot be made tight, and 
water from the inside of the stack leaks through, and corrodes and discolors 
the outside. With (c) the joints are easily filled with paint and made 
perfectly tight, so that corrosion is reduced to a minimum, 

Guys should be of not less than ^2 in. wire rope. Each guy should have 
a turnbuckle to take up slack and equalize tautness. The anchorage, whether 
"dead men" or buildings, must be such that there is no possibility of failure 
in the highest wind. The guj^s are attached to the stack either by eyebolts, 
with reinforcing plates inside, or by a guy-ring, carried around the stack in 
sections whose ends are bent out to form lugs. While the guy ring is the 
strongest construction when new, corrosion appears to concentrate about it, 
and so weakens the stack that the eyebolt method is perhaps the strongest 
permanently. 

The number of guys and their arrangement depends upon the height of 
the stack. Low stacks up to 50 or 60 feet may have one set of three or four 
guys. Over 60 feet, there should be two sets of four guys each, and stacks 
over 125 feet usually have three sets of four guys each. The upper or single 
set is generally attached to the stack about 12 feet below the top. When 
there are two sets of guys, the lower set is attached about 2/3 of the height 
from the ground to the upper set. When there are three sets of guys, the 
upper set is attached about 12 feet from the top, the lower set at about half 
the height of the upper set, and the middle set about half way between the 
upper and lower sets. 

Guys are commonly anchored at a distance from the base equal to the 
height of the guy band, so that they are stretched at an angle of 45°. When 
two or three sets of guys are used, the upper set may be arranged to form 
an angle of only 60° with the vertical. 

In congested city sections, stacks are often fastened to building walls by 
brackets or strap-iron anchors. Stiff guys may be made of 2 in. pipe for 
stacks up to 75 feet high, and of 3 in. pipe for higher stacks. All stiff guys 
should be well braced against Ijending unless they are very short. 

A guyed stack of >^-in. steel plate, built by the' Neii* York Central Iron 
JVorks, is shown in Fig. 103, It is intended for direct connection to the smoke 
flue. This stack has an inside diameter of 72' in. and is 104 ft. high overall. 
Each course is 5 ft. high and is made with lap-joints single riveted. At about 
40 ft. from the top a heavy ring is fastened to the stack, reinforcing it to 
receive the lugs for the guy wires. The top is finished with a steel band 
on the outside and reinforced with another band on the inside. 

Radial Brick Chimneys 

COMMON brick is seldom used for chimney walls except for small house- 
heating plants. Larger stacks have walls of vitrified hollow or perforated 
brick formed to occupy a certain position in the circular and radial lines of 
the chimney. It is said that the perforations in the brick form> a dead air 
space, which reduces the loss from radiation and pfevents sudden temperature 
changes within the stack. These radial blocks are larger than common brick 
and are made in sizes and shapes for all diameters. The method of laying 
and bonding as used in Hcinicke chimneys, and some of the shapes used in 
Custodis construction, are illustrated in Fig. 104. 

The brick are laid in cement lime mortar, with Yz in. joints, to give 
a straight batter or taper from top to bottom. The outside surface is 
invariably smooth while the inside surface sometimes has a series of steps, 
owing to the change in wall thickness of the different sections of the 
chimney wall. Starting with a thickness of one brick, or about 7 in., at 
the top, the wall thickness is increased about 2 in. for each section, 
which is generally 20 ft. high. A circular chimney 200 ft. high would 
have an actual thickness of 24 in. at the base. The wall thicknesses, m 



202 



CHIMNEYS 









Fig. 104. Brick Bond in Heinicke Chimney and Different Shapes of 

Custodis Radial Brick. 



Table 15. Outside Diameter Feet of Base of Brick Chimneys 



Height of 

Chimney 

Faet 



Internal Diameter at Top, Feet and Inches 



3—0 a— 6 4—0 4—6 



5—0 5—6 6—0 



ICM) 



to 
80 

85 



7.42 
7.80 
8.18 



7.69 
8.04 

8,38 



7.961 
8.27 
8.581 



8.46 
8.70 

8-95 



8.96 
9.13 

9-31 



9.96, 
10.02 
10.08! 



90 

95 



B.73 



S.5S 

" 9.19 
: 9.50 



•9. IS 
9.4:3 
9.67 



9.S.3 



10.13 

::».i9 



10. 



11.25 11.75 12. 



110 
115 



i;. 



10.20 
10.55 



10.03 
10.40 
10.77 



10.21 10 
10.60 10. 
10. 9S 11. 



07 



11.03 11. .50 11.95 12. 



h-' 



120 
125 

130 



10.79 
11.16 



10.55 10.90 
11J21 11.25 
11.65 



11.14 
11.50 
ll.SS 



11.37 11. 
11.75 11. 

12.1; 12. 



41 11.45 11. 
75 11.75 12, 



.50 12 



.55 12. 
,75 13. 



13.50 

13. 50 



14.OOS14.50 
14.22 14.69 



15.00 

15.15 



135 
140 
145 



12.05 

12.45 
12. S5 



12.25 
12.63 

13.00 



12.4: 1- 
12.S:' 12. 
13.15 13. 



22 13.2S 13. 



13.1 



73 14.0S 14.43 14.87 15.30 

i: 14. 5S 14.^- 1-.-3 15.45 

■ ---. '--..—. l^.^T 1'.;.; 15.60 



150 
155 

100 



13.25 
13. 5S 
13.92 



13.3S 
13.73 

14. OS 



13.5- 
13. J 

14.2: 



15.19 
15.43 



15. OS 15.42 15.75 
15.31^5.61115^)1 
15.55115.8116.07 



165 
170 
175 



14.25 1-=.^; U.: ; :-;."3 14. S6 U 
14.59 14. Tj U.— 15.11 15.26 1: 
14.92 1-5.13 15.:i3 1.5..50 1-5.66 15 



22 15.; 
49 15.: 
5S 15.-50 15.75.1':. 



15.66 

1 " C,"i 



15.78116.00116.22 
16.02'l6.20|l6.38 

16-25 16.40fl6.54 



ISO 
1S5 
190 



15.S0 16. 



16.50 16.65 16.80 
16.75 16.91 17.06 
17.00 17.16 17.31 



195 
200 

205 



:1 17..57 
" 17.S3 
: ::.16 



210 
215 
220 
22.=» 









1 - . - 










1 1:::: i 


::;: i;::: 






• • 1 


1 




' ! ii 











.50 
J3 



CHIMNEYS 



203 



9"-><^ 



"'^-Cement Head 
with W.I. Ring 




^U7'/2" 



4y4"Lining 






-I 






I 



F/ue 
Opening — 

WxZ"W.I.Ringat 
fooi of column and 
above and below 
the flue opening j 



Ur—l9'-6"-—^ 
k- 25'-e" -» 

Chimney on Octagonal Base 



,-->'• 



Wafer Table of 
(Neat Cement ^ 

I Beams over Flue WrSpace--' % 
Opening sufficient ^^ '"^ "^ 

to carry weigh f-^^ 



il8'/A 




-i 




^- 



V^OutDia.ie-Of'^ 

w--ie'-e" >J 

?5'-6"— 



Li 



->\ 






Chimney Round for Full Height 



Fig. 105. Example of Kellogg Radial Brick Chimneys. 



i 




Burnside Shops of the IlHnois Central Railroad, Chicago, 111. 
2590 H. P. of Heine Standard Boilers. 



CHIMNEYS 



205 



two styles of Kellogg radial block chimneys, are shown in Fig. 105. The 
batter indicated is based upon the figures in Table 15, from which layouts 
can be made for stacks 3 to 10 ft. diameter and 75 to 225 ft. high. The 
design should be checked to see that tension does not occur on the windward 
side, with the maximum wind pressure allowed, as the chimney would then 
be unsafe. 

It is common practice to use regular hard building brick for the base 
of the chimney, when it is of a sciuare or octagonal form. If the base forms 
part of the building wall, the two should be bonded by a slip joint, shown 
in the lower left-hand view of Fig. 106. The radial brick above the breeching 



f Cement Cap, 1-3 mh 



'/4''x5"m Retaining .. 
I^ing set in fuilt^ed ^ 
of cement mortar 




Outside Fitter Wall to 
protect beams from., 
atmosptiere. 

4'l. 

Concrete 2f- 
Flue Opening/ 



Head of Chimney 

Brick Lining,^ 



}>tinimum air space 
2' t^etween lining . 
and main wall 




f^;Lining Inside 
yofStacl< 

I I Beams on 
^Bearing Plates 



'^.fFi^eofArchfor 
each2'ofFtue 
Opening Widf- 



Builcting mil bonded 
mta base of chimney 
by means of slip Joint 




Plan of Octogonal Base 



Building Wall-. 




Section through 
Flue Opening 



Boiffle-Wall carried on I Beams 
2' below opening, to at least S' 
above flue opening For flue dia- 
meters ofS' and under, use 4" 
watlOverS'use 8"walt 




Square Base Forming Part of 
Building Wall 



Chimney Having Two Flue 
Openings Diametrically Opposed 



Fig. 106. Typical Details of Radial Brick Chimney Construction. 

entrance, shown in the upper right-hand view of Fig. 106, is supported by 
heavy beams on bearing plates with air spaces at each end to permit ex- 
pansion. The steel is protected against the effects of the gases of combustion 
by a flat arch. 

To prevent cracking, radial brick chimneys are provided with rein- 
forcing bands that take up the stresses due to expansion. One company 
conceals three or four 3 by 5/16 in. bar steel bands in the brick work. These 
rings are placed below and above the flue opening, ai or near the top of the 
lining and in the chimney cap or cornice. Another method is to place these 
bands at every change in wall thickness, omitting some of them when the 
bricks have corrugated sides. When gas temperatures are high, additional 
expansion rings are placed on the outside, spaced about 6 ft. on centers. 

A lining inside the chimney is also necessary as a further safeguard 
against expansion strains. This lining is independent of the stack and 
is separated from it by an air space of at least 2 in., which prevents the 
gases from coming in contact with the chinmey brickwork. For steam 



206 



C H I ^I X E Y S 



boiler plants the lining is made 30 to 50 ft. high, or about one-fifth the 
stack height. For very high gas temperatures the lining should be carried 
up at least half way, preferably to the full height. 

Expansion linings are made of ordinary fire brick or of perforated 
blocks about 4 in. thick. They are started 2 ft. below the flue opening in 
the stack. Sometimes the space between the lining and stack is covered 
at the top. One method is to corbel or rack out the shell of the chimney. 
This protecting ledge prevents soot or dirt from filling the air space. 

Ladders are also a necessar}' adjunct to chimneys. These are located 
either inside or outside for the full height of the stack. The rungs should 
be of ^ in. round iron, preferably galvanized, of "U" shape, spaced on 15-in. 
centers and securely anchored to the masonry. 

Lightning rods should be provided to protect brick chimneys. A number 
of pointed rods, above the top of the stack, are connected to one or more con- 
ductors extending down to a ground connection beneath the grade line. Points 
extending 6 to 8 ft. above the top are subject to rapid deterioration owing to 
the action of the outflowing gases. It is advisable, therefore, to locate a 
greater number of points around the stack so they will not project more 
than 6 ft. above the top. Less than two points should not be used on any 
stack. On large chimneys the lightning rods can be spaced from 6 ft. to 3 ft. 
on centers, on the outside circumference of the stack. 



23'-6'/4" — 

23'-2'/4'' — 

Cross Section 



J 




S'-e"- 

> 9'-0"High 
Plan 



Fig, 107. Soot Collector System in a Large Chimney. 



CHIMNEYS 207 



The lightning rods are usually made of %-in. copper, tipped with Yz-in. 
platinum thimble points. They are fastened to the masonry and are inter- 
connected by a copper cable placed completely around the top of the stack. 
To complete the circuit one or two bare copper cables, of ^ or 7/16-in. 
diameter, are connected to this ring. These conductors extend down the 
side of the chimney, where they are fastened at intervals, and terminate 
in a copper ground plate located in permanently moistened earth, in a 
charcoal bed, or in a pocket filled with crushed coke, and placed away from 
the chimney foundation. The grounding terminal can be of the coil, plate 
or cylinder t>'pe. 

For access to the interior of the stack and to facilitate cleaning, a 
cleanout door should be located in the base. Standard cast iron cleanouts 
measure 24 by 36 in. and are fitted with frames, hinges and latches. A 
tight fit is essential, so the contact surfaces should be planed. 

An effective method for the removal of soot and cinders from large 
chimneys is represented, according to Thos. S. Clark, by a collector system 
installed in a radial brick chimney 300 ft. high, 19 ft. diameter at the top, 
and about 23^ ft. at the base. Super-imposed hoppers. Fig. 107, are lo- 
cated below the flue opening in the base of the stack. These hoppers are de- 
signed to collect the soot and cinders dropped by the gases in passing up 
the chimney. 

The hopper floors are concrete lined with brick. Two are used so that 
the door in one is closed when the door in the other is open, to prevent the 
possibility of an open draft up the chimney through both hoppers. Access 
to each hopper is provided through a manhole, which is reached by a ladder 
on the outside of the chimney. Each hopper can be cleaned from a gallery 
built around the rim. In the chimney base are doors large enough to allow 
a cart to be backed in under the lower hopper to remove the soot and cinders. 



Reinforced Concrete Stacks 

THE advantages claimed for reinforced concrete chimne3^s are light weight, 
minimum space, strength, and rapidity of construction. All joints are 
eliminated, the stack and foundation being one monolithic structure. Patented 
steel forms are used rather than wood forms. The structural design is 
ordinarily based upon a maximum compression in the concrete of 350 lb. 
per sq. in. and a maximum tension in the steel of 16,000 lb. per sq. in. 

The details of a reinforced concrete stack 180 ft. high and 8 ft. in 
diameter, are shown in Fig. 109. The walls are considerably lighter than brick 
construction and are concentric with an even taper from top to bottom. The 
wall thickness is 5 in. at the top and 11 in. at the base. The concrete mix- 
ture is 1 part cement, 2 parts sand and 3 parts crushed stone or gravel. This 
is poured "wet" and then tamped in the steel forms and around the reinforc- 
ing bars to secure a thorough bond, as well as smooth inside and outside 
surfaces. 

Vertical reinforcing bars are placed about 3 in. from the outer surface 
and are distributed proportionately to the load. Around the circumference 
the stack is reinforced horizontally by heavy wire mesh, woven in triangular 
form. This is set close to the outside surface of the wall, as indicated in 
Fig. 108. The flue opening in the stack is also reinforced and the walls there 
are about 50 per cent thicker. 

Figs. 110 and 111 show the process of constructing a concrete stack. One 
view shows the steel forms and reinforcing rods in place, ready to receive 
the concrete mixture and the other the completed base section of the stack 
with the forms removed. The entire chimney is usually finished with a 
cement wash. 



208 



C H 1 -M X E Y S 



^-Wire 
Mesh 




^4 Layers of Bars 



Fig. 108. Base and Foundation of Heine Reinforced Concrete Stack. 

To protect the chimney column from the stresses due to expansion an 
isolated inner core or lining must be installed. This is built of firebrick or 
perforated blocks in the same manner as described for brick chimneys. 

Instead of the ladder steps used in brick construction, concrete stacks 
are equipped with tackle, consisting of a bronze pulley anchored to the top 
of the stack, and a 3 16-in, wire cable. 

A soot separator is an integral part of the reinforced concrete stack 
shown in Fig. 112. This stack serves a plant in which patent-leather is manu- 
factured. Soot and cinders issuing from the old chimne\- lodged upon and 
damaged the leather, which is dried in the open. The stack has an outside 
diameter of 8 ft. 8 in. at the top and 23 ft. 8 in. at the base. The unusual 
taper is due to the soot separator, which is built in at the base as part of 
the chimney. The soot separator, which consists of two concentric stacks 29 
ft. high, is made of radial brick. The separating chamber is in the outside 
circular passage while the inside section is the chimney proper, the two being 
connected by three openings in the wall. These openings are of sufficient 
area to handle the volume of gases through the 8 ft. area, which corresponds 
to the inside diameter of the chimney at the top. 

The flue gas entering the chimney through the 5 by 11 ft. breeching 
connection has its velocity reduced and owing to the shape of the passage, 
it flows spirally. This combined action separates the soot and cinders from 
the gas. which then passes up and out of the chimney free from ash. 

The outside wall of the soot separator also serves as the expansion 
lining for the chimney. The top of the separating chamber is closed with 
a cast iron cap. In the base of the chimne}' proper are two cast iron 
cleanout doors for removal of soot. A 2-in. perforated steam pipe has 
been provided. Tile drains, as indicated in Fig. 112, have been installed, to 
keep the chimney free from water. 



CHIMNEYS 



209 



■^8'-0'^-p\ 




Double layer of 
Wire Mesh 3'-0" 
below and above 
opening. Thickness I 
of waffs increa- 
sed 50%. 




Reinforcing at Smoke Opening 



Remforcing-- 




-25 '-P"- 



Fig. 109. Heine Reinforced Concrete Chimney. 



210 




Fig. 110. Steel Forms and Reinforcing Rods in Place to Receive Concrete. 




Fig. 111. Completed Base Section of a Concrete Stack. 



C H T ^t N E Y S 



211 




-Terra Coffa Drain 

^-2" Perforated Iron Pipe 
Terra Coffa Draln"^'^''^" ^'''^^ Opening 
Section A-A 



Triangular Mesh 
Horizontal Reinforcement 

3 Openings -5'-0"wide ty 15^6" high. 
Each placed as shown. 



Nofe:- 

Jy/o Cast Iron Clean-oof 
Doors where direcfec/ 
in base of stack 



flue 
Opening 

Radial 
Brick ' 



%<-2" 
i -Special Cast Irdh Cap 




w 

III 



! !i 



!' 



Li 






'illii'llr 



Over each open- 
ing in flue-l-6'x 
IZ25*IBeam 
4'^" long. Bent to 
circle of 4'0"Rad 



<S 



I'r 'l I 



I II In 

! Ill I 



m. 



■ Triangular Mesh 

^—^S/s"Sq. Tw. Rings 

__ Bend bars to 
'" accommodate 
flue opening 

^5 Extra Vertical Bars 

-5-%"Scf. Tw. Rings 



I III I 
iliiliilili 



Detail of Flue Opening 

~r\ ^ — 

Sectional Elevation 

Fig. 112. Soot Separator in a Rust Concrete Chimney. 



Reinforced concrete is sometimes considered in the experimental stage, 
but some concrete stacks have weathered the elements for 15 and 20 years 
without appreciable deterioration. One of the tallest chimneys is a reinforced 
concrete stack 550 ft. high with a wall thickness of 7 in. at the top and 
29^/2 in. at the base ; the average diameter is 32 feet. This stack is located 
in an earthquake country, Saganoseki, Japan, at about 450 ft. above sea-level. 

The Wiederholt chimney construction is "reinforced tile concrete." 
H'ollow tile blocks made of hard burned clay are used as the forms to receive 
the concrete during construction. The tile remains permanently as the inner 
and outer surfaces of the stack, surrounding the concrete at every point. 

Foundations for this type of chimney are made of concrete reinforced 
with horizontal steel bars running in two directions. Vertical bars are em- 
bedded to act as anchors for the chimney column. Around these vertical 
reinforcing bars the tile are set, each course being separately filled with con- 
crete. The horizontal rings are set in the concrete core. It is said that these 
chimneys are well adapted to chemical plants where acid gases occur and 
for other special service where gas temperatures are high. 




Pillsbury Flour Mills, Minneapolis, Minn., operating 5000 H. P. of 
Heine Standard Boilers. 



CHIMNEYS 



213 






7'/8V:<- 
I 






rii o 






/7"->^<- 

\ 



i — 

I 



> 



— /5 



T 



I 



Flue 
Opening 



^^ 



i^'^>j\ 



IT-O"^ 






^ 25'-0" >\ 

Original Brick Stack 

Fig. 113. Reinforcing an 




K 25'-0" H 

Stack Afier Concreting 

Old Brick Stack. 



214 CHI M X E Y S 



Remodeling of Chimneys 

T^RICK chimneys are increased in height b\- adding a gu\-ed length of steel 
^ stack. In some instances the added portion is built of radial brick. 
Where the old part is of square cross section, an octagonal adapting portion 
is worked in. Sometimes this work is done while the boilers are under fire. 

Bent brick chimneys can be straightened by sawing out mortar from the 
convex side. 

Chimneys that are dangerously defective ma}- be made safe by applying 
a casing of reinforced concrete. Fig. 113 illustrates an example. Steel 
chimneys that have become badly corroded may be renovated with a con- 
crete casing. 

Breechings 

I 'HE breechings or fmes should be so arranged as to offer a minimum 
-■- of resistance to the flow of gases. The area should be large enough so that 
a reasonable accumulation of flue dust will not cause any noticeable choking. 
The run should be as short and direct as possible. Connecting flues should 
be so designed that the entering gases tend to flow parallel with the gases 
alread}- in the main flue. Access doors should be placed conveniently to 
facilitate cleaning. 

Flues are frequently made 15 to 25 per cent larger in area than the 
stack, depending upon the amount of flue dust expected. Where fine fuel 
is burned with forced draft, the deposit of flue dust is relatively large and 
therefore liberal areas should be allowed. Builders of chimneys prefer to 
limit the area of fl.ue openings to 7 to 10 per cent greater than that of the 
stack. For structural reasons, the width of opening in the chimney should 
not be more than one-third the outside diameter of the chimney, the neces- 
sary area being obtained by increasing the height of flue opening. 

Sometimes the breeching area is proportioned to the total grate area 
served by allowing 22 per cent of the grate surface as the minimum' cross- 
sectional area of the flue. But this is not good practice, for the size of flue 
is entirely dependent upon the volume of gases to be dealt with, while the 
volume of gases due to any given grate surface varies with the intensity of 
the draft. A breeching suitable for a given grate area under natural draft 
may be far too small for the same size of grate imder forced draft 

The breeching area should be determined by gas velocity-. The draft 
loss depends upon the gas velocity in relation to the length, area and shape 
of the flue. The velocitj- may \a.ry from 15 feet per second for long 
rectangular flues of small area, to 35 or 40 feet per second for large short 
circular fl.ues. The draft loss maj^ be found by formula (10) on page 183. 
Whatever velocity is chosen, the resulting area should be increased sufficiently 
to allow for the deposit of flue dust. 

A breeching of circular cross-section causes less draft loss than a 
rectangular or square section, and the flatter the rectangle, the greater is the 
draft loss. This is clearly shown by the coefficients of formula (lO. Square 
or rectangular breechings with a semi-circular top are good designs. 

In practice, sharp bends and right angle turns are the most com^mon 
faults found in breechings and smoke connections. While it is not difficult 
to make or connect long-sweep turns and to install necessary- deflectors, 
these details may be neglected unless the work is carefully supers-ised. 
Space conditions often make the installation of some bends necessan.-. The 
designer must then use the least number of bends and make them as long 
and gradual as possible. The bends necessary for a change in direction 
should have an inside radius at least equal to lj'2 times the diameter or 
width of the breeching. 



CHIMNEYS 



215 



Fig. 114 will emphasize the bad effect of sharp gas turns. The entering 
gases tend to strike the opposite wall and leave eddies as at A, A, which 
are the equivalents of reduction in flue area. Rounded corners at X and 
near A would reduce the draft loss, but the gases from Boiler No. 1 would 
still interfere with the flow from Boiler No. 2. This figure also shows poor 
design in making the breeching parallel. The gases from Boiler No. 2 lose 
velocity in filling the larger area of the main flue, and as this velocity has 
been given to the gases by the effect of the chimney, velocity so lost is wasted 
chimney effort. As the gases from Boiler No. 1 crowd into the main flue, 
the gases from Boiler No. 2 have less space and their velocity is again 
increased, putting more work on the chimney. 



To Stack 





From Boiler 
No. I 



From Boiler 
No. 2 



Fig. 114. Effects of Right-angle Turns in a Smoke Flue. 

Fig. 115 illustrates excellent practice in designing a breeching to serve 
several boilers. The bottom of the sides is made horizontal to agree with 
the boiler settings, and the increase in area as each boiler is connected is 
taken care of by the sloping top. The deflection plates forming the bottom 
are made parallel with the top, keeping the gas velocity uniform, and the 
steps between them provide ideal locations for the pampers. 



I r>^ t/ce 




Fig. 115. Breeching and Damper Arrangement for a Battery of Boilers. 

A good example of breeching design for several boilers is shown on 
page 218. 

The connection to the stack should be through an easy upward bend, 
so as to enter the chimney at about 45 degrees. 

Where breechings from boilers on both sides of a chimney meet before 
entering it, care should be taken to guide the two currents into fairly 
parallel streams before they meet. Fig. 116 is given to emphasize the bad 
effect of two opposing gas currents in a bull-headed or T-connection. To- 
gether with the area-reducing eddies at A, A, as in Fig. 116, this head-on 
collision of the two streams may cause sufficient draft loss to reduce the 
boiler capacity seriously. 




Equitable Building, New York City. 

3500 H. P. of Heine Standard Boilers. 

Tallest Chimney in the World. 



CHIMNEYS 



217 



f^rom 
Boiler No. I 




A 



r 







From 
'Boiler No. 2 



Fig. 116. 



7b Stack 
Effects of Bull-headed Connection on Gas Flow in Breeching. 



In such instances curved deflecting plates as at X, particularly when a 
dividing plate is carried from X to the entrance of the flue leading to the 
stack, have made a notable improvement. Rounding the corners as at A, A, 
is a still further advantage. 

Fig. 117 shows two flues connected to a central stack. To reduce the 
draft loss from the head-on collision of the gases, a baffle is placed in the 
base of the chimney, so that the gases are deflected into parallel directions. 



From _ 
Boiler No. I 




From 
Boiler No.? 



''Stack 
Fig. 117. Baffle Wall in Chimney to Prevent Collision of Gases. 



Examples of good practice in breeching design where the chimney is 
carried by a symmetrical hood are illustrated by Figs. 118 and 119, which 
show breeching hoods for one and two boilers respectively. 

As most engineering problems are solved by compromise, so the power 
plant designer must frequently compromise between ideal flue design and 
increased height of stack. Flat rectangular breechings and sharp curves may 
become necessary to meet space restrictions, and the increased chimney 
height resulting therefrom must be accepted as imavoidable. 

Steel or iron plate is used in constructing breechings and smoke connec- 
tions. For main breechings of square section, metal 3/16 in. thick is required. 
The sides, bottom and top are braced or reinforced on the outside with 
2^-in. angle iron. Individual smoke connections between boilers and 
breeching are usually made of No. 10 gage metal, although for longer runs 
and large size boilers No. 8 gage plate is sometimes used. When of square 
section, these are held at the corners by l-V4-in. angle iron, and are also 
reinforced or further stiffened with angle iron on the outside. 

For the removal of soot accumulation and for access to the breeching, 
cleanout doors should be provided at convenient points. It is good practice to 
install one cleanout at the far end of the breeching and at least one other 
cleanout along the run of flue, either in one side or at the bottom. Clean- 
out doors are made of heavy cast iron or steel plate, fitted with massive 




•d 

V 



CO 
Wi 

CO 

US 
u 



CO >— I 

>o 

t-i C0 

O T) 

_r ■♦-' 

TJCO 
CO i; 

^ o 



3 
G 

IS 

u 

(U 



PQ 



CHIMNEYS 



210 







Fig. 118. Ideal Breeching Arrangement for Single Boiler. 




D ampers 




Boi/er A/o. / *//>* 3 oiler No. 2 

Fig. 119. Ideal Breeching Arrangement for Two Boilers. 



220 CHIMNEYS 



hinges and one or two clamps to facilitate opening and closing of the door. 
iJoor frames are riveted to the breeching ; both the frames and doors 
should be planed so as to be air-tight. Sliding doors are sometimes used 
for cleanouts. 

Breechings and smoke flues should be covered with non-conducting 
material, such as asbestos or magnesia heat insulation, or else be protected 
with refractory brick or other vitrihed material. The coverings or linings 
are frequently placed inside the breeching to protect the metal against 
the possible corrosive action of the gases, although it is advisable to have 
the insulation or lining on the outside. The breeching, smooth on the 
inside, will then permit a straight uninterrupted liow of the gases into the 
>moke stack; there will be no loose pieces to fall into the breeching and 
obstruct the gas passage, and repairs can be made without interfering with 
plant operation. The insulation on smoke fines is important because it pre- 
vents lowering the gas temperature, by reducing heat losses. If this temper- 
ature is lowered while the gases are passing through the flue, the effective 
draft will be reduced. 

Overhead steel breechings are usually hung from the building construc- 
tion, although special supports are frequently required. 

Underground flues involve a high friction loss because of the large num- 
ber of turns in the gas path from the boilers to the stack. The brick 
or concrete used for these flues is porous, so that the flue is subject to leak- 
age. Being located below the boiler room floor the flues are difficult to keep 
clean and the soot gradually accumulates and obstructs the gas passage. 



Dampers 

T^AMPERS are used both to vary the gas flow in controlling the rate of 
'^ coml)ustion, and to close the flue entirely in isolating idle boilers. Dampers 
should move easily and when wide open offer the least possible resistance to 
gas flow. 

Dampers used for isolating idle boilers or flues should be reasonably 
gas-tight. Levers or handles to operate dampers should be located in par- 
ticularly convenient and easily accessible positions, and be so arranged that 
they definitely indicate how wide the dampers are open. 

Dampers should be made the full area of the breeching or uptake. If a 
rectangular damper is used, it will cause the least disturbance to orderl}- gas 
flow if swung about its longer axis. Fig. 120, for a rectangular damper 
turning about its shorter axis, illustrates faulty design by showing the area 
wasted in the formation of eddies. Fig. 121 illustrates good practice in 
damper arrangement. The dampers swing in unison about their longer axes ; 
and when wide open, the gas flow is virtually undisturbed. 

Each boiler must be provided with an independent damper. It should 
fit well, so that when the boiler is idle there will be very little leakage. 
Inleakage of cold air into the main flue through defective dampers of idle 
boilers reduces the draft very seriously. 

Individual boiler dampers are set by hand so as to divide the load 
equally between the boilers by correcting the unavoidable differences between 
the drafts at boilers near the stack and those at boilers more remote. Varia- 
tions in the general or total load are cared for by a main damper near the 
chimney, controlled either by hand or by an autoinatic regulator. Damper 
regulators are discussed in Chapter 16 on OPERATION. The main damper 
need not be tight unless there are more than one. such as when two or more 
flues enter the same chimney. Sometimes the main damper is prevented from 
forming a tight closure, either by providing a hole in it, by stops to limit 
its travel, or by adjustment of the operating mechanism. 



CHIMNEYS 



221 



Br««,chin3--> 




Fig. 120. Faulty Damper Installation. 




Operating 
-^ Lever 




Fig. 121. Proper Location of Dampers, 



799 



CHIMNEYS 



Dampers should be balanced and should move easily. Swivel or "butter- 
fly" dampers are generally used, since they swing freely and are not apt to 
get out of order. Sluice or slide dampers are sometimes necessary- to meet 
space requirements, but are avoided wherever possible, as they are difficult 
to move, especially when there is dust in the slides or the dampers are 
slightly warped. 

Dampers are operated by chain, wire rope or rods. Rods are preferable, 
because they give positive action, whereas if chain or rope is used, reliance 
must be placed on the overbalance for movement in one direction. If any 
of the bearings stick, the damper may remain in one position without the 
defect becoming immediately known ; whereas rods show such a trouble at 
once. For this reason, where rope or chain is used, the overbalance is made 
much heavier than is generally necessary, thus making movement more 
difficult. 

Unless the handles for operating the dampers are brought to a con- 
venient position, so that the attendant can work them, easily, they will not 
be adjusted as frequently as they should be, and waste of fuel will result 
from failure to relate the draft to the load and the fuel. The bad effects 
of controlling the draft by means of the ashdoors and tiredoors are fairly 
well known, but blame for this condition should usually be placed on those 
responsible for making damper operation difficult and awkward. 

The handles should be arranged so as to definitely indicate how much 
the damper is open. This indication is sufficiently important to warrant 
checking from time to time. Lost motion prevents correct indication and 
should be eliminated, either by overbalance or refitting. The damper shaft 
should be squared where the operating lever is attached to prevent any 
possibility of slipping. The same requirement applies also to any other shaft 
and lever of the operating mechanism. 

Fig. 122 shows the construction details and general proportions of a good 
damper design. 



.■S/8' Rivets 



SV 



3 3 3 3| 3_ 



35 



-<r--r2' 1 .r Round 




Sotted hole in 



-5V-5:7^:7T- 



w— — ■ — ^ 



4'x 5'x^' Angle- ' 
Fig. 12 2. Construction Details of a Damper. 



Steel plate ^i-in. thick down to Xo, 8 gauge is used for dampers. Angle 
iron shapes are emploj-ed as ribs for large surfaces, set about 2 ft. apart. Bar 
iron or extra heavy pipe is used for the spindle which is supported on rollers 
or even ball bearings on the outside of the steel flue. 



223 



CHAPTER 7 



MECHANICAL DRAFT 

MECHANICAL draft is adopted for obtaining economy of operation, in- 
creased capacity, or both. It is called either forced or induced draft, 
according to whether the draft is intensified by increasing the pressure 
at the inlet or decreasing the pressure at the outlet of the boiler. Both 
methods, and the combination of the two, are in general use. 

Forced draft may be of the closed ashpit or closed stokehold system; 
but as the latter is confined to marine practice, it will not be discussed here. 
The economic advantages resulting from the use of mechanical draft are 
best explained by diagrams. In the following diagrams the pressures and 
vacua are not drawn to scale, but they clearly indicate the efifect of the 
different ways of applying mechanical draft. 

Fig. 123 represents graphically the circumstances present in natural draft 
plants. 




Fig. 123. Diagram of Natural Draft Plant. 



The vacuum in the boiler setting and flues draws in cold air through the 
porous brickwork, cracks, leaky cleaning and dusting doors, and through 
firedoors opened for hand firing. The heavily shaded area indicates where 
the greatest heat loss occurs, due to the large quantity of cold air reducing 
the temperature of the gases and rate of heat transfer to the water in the 
boiler. The lighter shaded area shows the draft loss through leaky flues, 
which reduces the static chimney draft by lowering the gas temperature, and 
reduces the available draft by increasing the volume of gas to be handled by 
the chimney. 

Fig. 124 shows the conditions when forced draft is applied to take care 
of the draft resistance of the fuel bed. 

The vacuum in the boiler setting and flues is much less, so that the 
inleakage of cold air and consequent waste of fuel is greatly reduced. Very 
little cold air is drawn in through open firedoors, as the vacuum above the 
fire is extremelv small. 



224 



M E C H A X r C A L D R A F T 



Fuel Bed Bo/^er Seff//?^ f/ues Chimnei^ 




Fig. 124. Diagram of Forced Draft Plant. 

A further economy may be gained by the use of cheaper fuels which 
generally offer much greater draft resistance, since there is no reasonable 
limit to the air pressure which va^x be maintained in the closed ashpit. 

When forced draft is used for increasing boiler capacity, an operating 
limit is set b}- the capacity of the chimney, and to pass this limit, induced 
draft must be used as well. Fig. 125 shows how the condition illustrated by- 
Fig. 124 is modified bv the addition of the induced draft fan. 



( f 

K fuel Bet/ Boiler Seff/ng 



FJues I /^/7 C hjmrjet^ 




Fig. 12 5. Diagram of Combined Forced and Induced Draft Plant. 



Even under these intensified conditions, the loss as shown by the heavily 
shaded area is less than under those for the natural draft of pig. 123, because 
the vacuum over the fire is so small. 

The dotted lines in Fig. 125 show what happens when the operating 
limit of forced draft alone is passed. As the chimnej' is overloaded, it cannot 
cause sufficient draft to overcome the resistance of the setting and flues at 
this higher capacity, and the forced draft builds up pressure above the fire. 
This pressure continues through a part of the boiler setting as shown by 
the dot-shaded area. Where this pressure occurs, the gases escape through 
leaks into the boiler room, causing great discomfort ; brickwork, furnace 
fronts, firedoors, and so forth, deteriorate rapidly. While tlie draft resistance 
of the fuel bed is unchanged, the ashpit pressure, which is measured above 



MECHANICAL DRAFT 



225 



atmospheric pressure, is higher than when the induced draft is added. There- 
fore, the cost of operating the induced draft is somewhat offset by the 
reduction in cost of operation of the forced draft, due to the lowered ashpit 
pressure. 

Induced draft alone is not generally applicable for increasing boiler 
capacity. Fig. 126 illustrates how it increases the leakage loss in compari- 
son with Fig. 123, which is represented by the dotted curve. 




Fig. 126. Diagram of Induced Draft Plant. 

When economizers are installed, the temperature of the chimney gases 
is reduced, and the resistance of the economizer is added to those of the fuel 
bed, boiler setting, and so forth, and the natural draft of the chimney is 
often rendered insufficient to carry the desired load. This defect of draft 
may be made up by induced draft fans. Fig. 127 is a diagram illustrating the 
addition of an economizer and induced draft fan to the plant as shown in 
Fig. 123. 



1 


Fuel Bed 


Boi/er Setting 
Atmospheric Pressure 


F/ues 


fconemijer 


ran 


CMmnet^ 






1 
1 


1 


1 




/ 


_^^'' 




5 
3 

3 

VI 

1 


V 


1 


k 
1 





Fig. 127. Diagram of Economizer and Induced Draft Plant. 

As shown by the dotted line from Fig. 123, the induced draft fan just 
makes up the draft losses due to the resistance of the economizer and the 
reduced static chimney draft occasioned by the lowered gas temperature. 



M E C H A N T C A L D R A F T 227 



There are two ways of producing mechanical draft in common practice, — 
by fans and by jets. Each method has its advantages and is better suited to 
some conditions than the other is. Fans usually take much less power to 
operate than jet-blowers, because the simplicity of jet-blowers has resulted 
in their haphazard manufacture. However, A. Cotton states that steam jet- 
blowers whose power consumption compares favorably with that of fans are 
made ; although ill-proportioned and wasteful blowers are widely offered. 
Jet-blowers have nothing which can break down or wear out, so that in 
reliability they are not approached by fans. Furthermore, they cost less and 
need no foundations. On the other hand, the steam used by jet-blowers is 
lost, while that used by fan engines or turbines may be recovered in feed- 
water heaters or condensers. The steam of jet-blowers, by raising the posi- 
tion of highest temperature, keeps the grate bars cooler than usual and tends 
to reduce the formation of clinker. 

Disk fans mounted on the same shaft with steam turbines are used for 
low pressure forced draft work, generally a separate fan to each boiler. 
Owing to their extremely high speed, sufficient pressure is generated to give 
fairly high combustion rates. In some types, the turbine exhaust is discharged 
into the ashpit ; in others the turbine is fully enclosed, and the exhaust may 
be recovered by condensation. 

The best examples of jet-exhausters for induced draft are offered by 
locomotives and by the evase chimneys mentioned in Chapter 6. 

Forced Draft 

THE first considerations in designing a forced draft installation are the 
quantity of air required and the pressure. It is common to allow either 
12 cubic feet per minute per B.H.P., or 18 lbs. of air per pound of coal. 
These figures should not be used indiscriminately, as the air required will 
depend upon the kind of coal and the method of burning it. For stoker 
work, fans should be capable of furnishing 50 per cent excess air above the 
theoretical amount. The pressure required will depend upon the kind of 
coal to be burned and upon the rate of combustion. Reference should be 
made to Fig. 97. In stoker firing, the stoker manufacturer should be con- 
sulted, since the pressure necessary to generate a given boiler capacity differs 
greatly with different types of stokers. With fans, great care should be 
taken to get these quantities as accurate as possible, for if the fan proves to 
be improperly proportioned for its work, it cannot be changed without con- 
siderable expense. With jet-blowers, more latitude is offered, since changes 
in the size of nozzles are readily made. But the characteristics of any jet- 
blower under advisement should be carefully considered, as it is the lack of 
such consideration that is responsible for frequent waste of power. 

Forced draft pressures have increased rapidly in recent years. A few 
years ago, pressures above 2 in. of water were not called for. Such 
pressures as v.ere used were met by fans driven at slow speed by engines. 
At present, underfeed stokers developing high boiler ratings need pressures 
up to 8 in. of water, and the higher fan speeds necessary have caused the 
engine to give way to the more dependable steam turbine or electric motor. 

The principal resistance against which the forced draft fan must operate 
is offered by the fuel bed. This is changing constantly, varying the pres- 
sure and the volume of the air delivered by the fan. The fan speeds 
are usually controlled by an automatic device and are continually changing. 
The pressures required from the fan vary with the boiler load, from 1 to 8 
in. of water. The speeds of the fans are high and they require con- 
siderable strength. Because of the changing speed, the fan impeller must be 
strong enough to resist not only centrifugal forces, but also stresses caused 
by the changes in torque. 



228 



^[ K C H A X I C A L 1 ) R A F T 



Forced draft fans built by different manufacturers differ considerably in 
size. The dimensions in Table 16 are given as an example. 




Table 16. Sizes and Weight of Forced Draft Fans 



Boiler Output, jFan Outlet Area, 
H. P. ' Sq. Ft. 



INCHES 



Weight 
Complete, 

Lb. 



500 
1.000 
1,500 


4.3 

8.6 

13 


55 
77 
95 


50 

68 
80 


43 
61 
74 


1,700 
3.300 
4.800 


2.000 
3.000 
4.000 


17 
20 
24 


110 
135 
155 


94 
115 
129 


86 
105 
122 


6.500 

9.000 

12,000 


5,000 
10.000 
15.000 


43 

86 

130 


174 
246 
300 


145 
195 
233 


136 
192 
236 


15.000 
20.000 
45.000 



Fan Driics. Forced draft fans, whether automatic regulator is used 
or not. should be driven at variable speed. The most satisfactory method 
is by steam turbine. For the smaller fans (capacity about 25.000 cu. ft. per 
min.) good steam economies can be secured with a direct connected turbine. 
For volumes in excess of this helical gears should be installed between tur- 
bine and fan. 

The direct-current motor with a speed reduction of 50 per cent, is well 
adapted to driving fans. The reduction should be tirst accomplished by 
field control, then at the lower speeds by armature control. The speed con- 
trol is important as the horsepower of a fan operating against a given re- 
sistance changes as the cube of the speed. 

In large power plants power for auxiliaries is often furnished by a 
turbine-driven alternator ; this is not an advantage, as far as the fans are 
concerned, because alternating current motors are not efficient at reduced 
speeds. This motor is preferable, however, when the fans are to be placed 
in a boiler house or other part of the plant where the commutator of the 
direct current motor would be exposed to dust and dirt. 



MKC II A N I CAT. DRAFT 



229 



Opcraiin^^ Difficidlics. A properly designed forced draft fan should be, 
and usually Is, one of the most reliable pieces of apparatus in the power 
plant. However, certain troubles and difliculties are encountered more fre- 
quently than necessary. Oil escapes from the fan bearings, being picked upby 
the entering air and carried into the fan impeller. As fan bearings are ring 
oiling the oil reservoir may become empty and cause the loss of a bearing 
lining or shaft. 

The fans may fail to deliver the required volume at the necessary 
pressure. This reduction in pressure may easily occur even with fans 
that will meet their guarantees when tested on the manufacturer's test 
plate. This discrepancy is due to the difference between the test and installa- 
tion conditions. On the test plate the fan is connected to a long straight 
duct. Very seldom is any such arrangement found in an actual plant. 
Whenever possible a layout of the duct work leading to the fan should be 
given the fan manufacturer, and he should be asked for approval and recom- 
mendations. 

The lack of proper balance is the most serious difficulty encountered 
in fans. If this is allowed to continue, the metal in some part of the fan 
impeller will be fatigued to the point of rupture. Out-of-balance is largely 
in the control of the manufacturer, but is occasionally caused by negligence 
on the part of the operating force. All fan wheels will accumulate dust and 
should be cleaned regularly. Ordinarily a forced draft fan that is cleaned 
every two months will not accumulate sufficient dirt to impair its running 
balance. 

Types of Fans. Fans may be classified according to the style of blading, 
whether backwardly curved, radial, or forwardly curved. Characteristics of 
each type are given in Figs. 128, 129 and 130. The behavior of these different 



ZOO 100 10 

180 SO 9 

160 80 8 

140 70 ^7 

IIOO'^.SO 05 
o >^ :5 

D. O g 

% 80 g40 -o4 

3:^ 60 it: 30 ^3 

40 ZO"^? 

20 10 1 









Sf-Q 


f/'c A 


^r. 




























"^^ 


^ 


»s.. 




























\ 


\ 


H' 


)rsef. 


■)owe 


r 














r\^-^^ 


y_^^ 






■^ 


«Sfc 








^ 


7^ 




^^ 






xO^ 


£ 


i>^ 


-^ 








\ 


^v 












^ 


X^ 


r 












\ 


\ 








yf 


y^ 


















S\ 


i 






/ 




















N 


\ 




























\ 




1 
























N 


\ 



10 20 30 40 50 60 70 80 90 100 110 120 130 WO 
Air Flow,Thousandsof Cu.Ft.perMin. 

Fig. 128. Pressure Characteristics of Backwardly Curved Blade Fans. 



types determines their applicability to meet the particular problem under 
consideration. The conditions imposed by hand firing and by each of the 
various types of stokers are different, and" the demands of each at different 




Mccormick Building. Chicago, 111., equipped with Heine Standard Boilers. 



MECHANICAL DRAFT 



231 



?Z0 1?0 12 

210 no II 

200 100 10 
180 90 9 
IGO 80 8 

4- S- 

140 §70+^7 
o o 

IizocSgoJg 

o -c o 

glOO §50^5 

80 t 40 ^'4 
GO 30 o3 
40 20 2 
20 10 I 

° ° °0 10 20 30 40 50 GO 70 80 90 100 110 120 130 140 150 160 

Air Flow .Thousands of Cu.Ft per Min. 

Fig. 129. Pressure Characteristics of Radial Type of Fans. 





























y 


y 




























y 


X 
























,«<■/ 


/ 












6fc 


7 fie Press 


^2, 








M< 


f\ 


y 


























■->< 


> 




























A 


y 


"^ 


\ 


















(A 


■A 




^ 






"^ 




\ 


s. 












,vO 




y 


/ 












s 


"^ 


s. 










I 


X 


r 


















\ 


L 


i 


y) 


f 
























\ 
































^ 


\ 




1 




























\ 


^ 



loads are different. The pressures required at different loads must therefore 
be compared with the fan characteristics to determine which type of fan 
will be appropriate. 



240 120 12 
220 110 II 
200 100 10 
180 90 9 
160 80 8 
1405 70 d7 
|l20'j60'fe6 

c* c ^ 

12100 .5! 50 -g 5 



80Ci40:t:"4- 
60 30"^ 3 
40 20 2 
20 10 I 





























/ 






























/ 


/ 




























J 


/ 












\ 
















<^^ 


/ 
















\ 




i 


^01 fie 


Press 


jre 


—/ 






























y 


7^ 




'^ 


^. 
















\^'f- 


P^ 




f*^ 






^^ 


^ 


\ 


V 












,{> 


r 


y 












s 


\ 


\ 


s^ 








■3- 




y 


















\ 


s. 


\ 






/ 


r 






















p\ 


sN 




/ 




























\ 


\ 


/ 




























^ 



10 20 30 



40 50 60 70 80 90 100 110 120 130 140 150 
Air Flow,Thou sands of Cu.Ft. per Min. 

Fig. 130. Pressure Characteristics of Forwardly Curved Blade Fans. 



2Z2 ^I E C H A X I C A L D R A F T 



For use with stokers, there is a temptation to pick a small fan and accept 
a poorer efficiency for the peak loads, especially when they occur for only 
a short time each day. Whether this is good economics will depend upon 
the frequency and duration -A the peak loads. There is always danger that 
the tip speed of the fan so selected will be too high at the peak load. Fans 
are designed for a safe tip speed of 16,000 to 18,000 ft. per min. An excellent 
specification requirement is that the fans shall be run without showing any 
signs of permanent distortion for two hours at a speed 25 per cent above 
the highest operating speed. As stresses due to centrifugal force increase 
as the square of the speed, the stress during the two-hour run will be about 
50 per cent greater than under the most severe specified condition. This test 
can be met by an}^ properly designed fan without causing harm to show up 
then or later. Tests at higher than 25 per cent overspeed should not be 
called for, as the stresses put upon the fan might be great enough to start 
ruptures, which might escape inspection after the test run. 

Pcrfoniiance of Fan. A test on a manufacturer's test plate with the 
fan blowing into a long straight duct is simple enough, although it requires 
extreme care, but to test a fan after installation is extremel}^ difficult. The 
only readily available instrument for measuring the volume of air in a duct 
is the double pitot tube. Fig. 131 shows this tube and its connections to the 
indicating gages. When the pitot tube is carefully used, volumes can be 
determined within 2 per cent accuracy. To secure this accuracy, measure- 
ments must be made in a straight run of pipe far enough away from the 
fan so that the turbulence it sets up in the air is dissipated, and a smooth 
steady parallel flow is insured. Usually the distance from the fan outlet to 
the pitot tube should equal 10 or 15 pipe diameters. In most forced draft 
installations there is no straight pipe of this length, so that the results must 
be regarded as indeterminate. The readings with a pitot tube are sometimes 
surprisingly accurate, even when it is placed close to the fan outlet, but never- 
theless one should always select as a place of measurement the longest run 
of straight pipe available. 

The volume delivered by the fan can be determined from the manufac- 
turer's pressure, volume and horsepower-volume curves, drawn for the 
speed at which the fan is tested. The pressure can be determined by taking 
five or six readings at different places in the main duct, allowing about Vio 
in. for the loss from the fan outlet to the main duct. The volume corre- 
sponding to this pressure can be determined from the pressure-volume curve. 
If the fan is driven b}^ a motor so that the horsepower can be determined 
for the same conditions an additional check can be secured from the horse- 
power-volume curve. The volumes determined by pressure and b}^ horse- 
power should check within 5 per cent. 

When the air velocities are measured by a pitot tube, the duct must be 
divided into at least 16 equal areas and a reading taken at the center of each. 
In obtaining the average of the 16 readings of velocity pressure, the veloci- 
ties can be calculated for each reading and the average then determined ; 
or the average velocit}' pressure can be calculated by squaring the mean of 
the square roots of the 16 readings. 

The pitot tube shown in Fig. 131 is double. The small inside tube is 
open onl}^ at the end, which must point directly and truly into the air stream. 
The pressure indicated on a U tube with one leg connected to this inner 
tube and the other leg open to the atmosphere, is the static pressure in the 
pipe plus the velocity pressure. The larger outside tube is plugged at the 
end and has four 0.02 in. holes drilled perpendicularh' through the sides. The 
pressure indicated on a U tube with one leg connected to this outer tube 
and the other leg open to the atmosphere is the static pressure in the pipe 
only, since because of the small perpendicular holes, the pressure is entirely 
independent of the air velocity. The difference between these readings is the 
velocity pressure. If, instead of connecting U gages as just described, the 



.AI E C H A X I C A L D R A F T 



233r 




4 Holes in Outer 
.'Tube only 0.02" Dia. 



\\\\\\\\\\\\\\\V.\\'\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\V\V' 






vyyy///y'yyy/^/yyyyyy^yyyyy/y>//y///yy^y///yy^y/yyyy/'yyyy/yy/yyy/^^^ 



wvwwvwwwvwvv x's^:^?^^ 



s^\V\\\V^VVV V\VVs\V\^\\W 



Fig. 131, 



-Not Less Than 2'^ ^-^/je"-^- 2^/6"- 

A Double Pitot Tube for Measuring the Volume of Air in a Duct. 



inner tube of the double pitot tube is connected to one leg of the U gage, and 
the outer tube to the other leg, the reading of the U gage will now be the 
velocity pressure, since the static pressure is applied to both legs of the 
U gage and is thus canceled. 

The velocity can be calculated from the velocity pressure by the follow- 
ing formula : 

C13) 



V= 1096 P 

\ zc 

V = velocity, feet per minute. 
p =z velocity pressure, inches of water. 
zv = density of air in pipe, pounds per cubic foot. 
At 65 deg. and standard barometric conditions, the density of air is 
0.075 lb. per cubic foot. The above formula is readily derived from 

J'l=2gh (14) 

/ 1= velocity, feet per second, 
o- 1= 32.2 =1 acceleration due to gravit}^ 
/i =: head, feet of air (equivalent to }> in inches of water). 




O u 
- O 

>.« >> 

^^ 
S ci, 
c b 

CO -j; 

3 ^ 

u 

u o 

•^ u 
CO 



u 

^ 



C 
CO 

oco 

"—I u 

. c 
o o 

«^ 



CO 

a 



MECHANICAL DRAFT 



235 



The horsepower represented by the air leaving the fan, usually called air 
horsepower, is the fan output and can be calculated from 

//.P. = 0.000,158 Qp (15) 

Q 1= volume, cubic feet per minute. 
p := pressure, inches of water. 

If this fan output is used to determine the mechanical efficiency of the 
fan, p should be the total or impact pressure ; that is, the sum of the static 
and velocity pressures, which sum is given by the reading at the small open 
end tube. If the static efficiency is to be found, the fan is not credited with 
the energy due to the velocity of discharge, and p should be the static 
pressure, or the reading given by the large outside tube. The quantity of air 
handled per minute by forced draft fans is frequently a large percentage of 
the cubical contents of the room in which the fans are placed, so that not 
infrequently the static pressure in the room is 0.2 in. below atmosphere. This 
condition will automatically be taken care of by the readings of the U 
tubes themselves, provided they are always placed in the same room from 
which the fans are exhausting their air. 

Ducts and Dampers. The shape and arrangement of ducts and the plac- 
ing of dampers has an important effect upon the pressure of the fan as car- 
ried through to the stoker windbox. Bends should have an inner radius of 
from 1 J/2 to 3 diameters. Y's should be used in preference to T's, and if T's 
are necessary the "Poor Type" of Fig. 132 should be avoided, if possible, or 
the sharp corners changed to be like the dotted lines. The one marked 
"Good Type" v/ith rounded corners and deflecting plates is preferred ; and if 
the ducts are of rectangular cross-section, the deflecting plates are easily 
applied. 



t t 



t t 



/ 




PoorTyp« Good Type 

Fig. 132. Good and Poor Forms of Tees. 



Dampers. When two or more fans blow into a common duct, outlet 
dampers for each fan must be provided; these can be closed when any fan 
is not in operation. These dampers frequently cause large reductions in 
fan pressure. An ordinary butterfly damper should have a small indi- 
cator placed parallel to the damper and fastened to the damper shaft outside 
the duct, whenever the damper handle itself will not serve as an indicator. 
When the handle can be placed in a position other than parallel to the 
damper itself no one can be sure when the damper is open. The butterfly 
damper should be placed as far from the fan as is convenient. Its shaft 
should lie in a plane perpendicular to the fan shaft; that is, the damper 
shaft should always be vertical rather than horizontal. 

Louver dampers are frequently placed in or close to the fan outlet. 
The shafts of these should also be provided with an indicating mechanism. 
They should be vertical, particularly with the small housing types of 
fans. The air in the fan outlet is in a highly turbulent condition due to the 



236 M E C H A X T C A L D R A F T 



action of the wheel and does not come from the outlet in parallel lines 
and with even velocit}* distribution. When louver dampers are used in 
the fan outlet with horizontal shafts arranged parallel to the fan shaft, 
the pressure readings taken beyond the damper will invariably show that 
the best position of the damper is parth- closed and not wide open. If the 
shafts are vertical, the damper in its wide open position will always offer 
the least restriction, and the resistance will be less than in any position with 
the horizontal shafts. 

Screens for forced draft fan inlets should always be provided. Serious 
accidents have occurred in instances where the arms and legs of attendants 
have been drawn into contact with the impeller. These screens sometimes 
present a serious obstruction; but they need not be heavier than 5^-in. wire. 
nor closer than 2-in. mesh. There have been occasions when inlet screens 
made of ordinar>- expanded metal have offered a resistance sufficient to cause 
a 1-in. drop in pressure in the fan inlet. 

Air Leakage in Ducts. All ducts carr5-ing air under pressure must be 
tight. The leakage that can occur in ordinarj" ducts is seldom appre- 
ciated because the air cannot be seen. Air will leak through joints much 
more easily than water will. The pressure on a forced draft duct may be 
6-in. of water, representing a head of air of 416 feet. In carrying water 
at a head of this magnitude the utmost precautions would be taken to keep 
the ducts tight, but with air the importance of this point is apt to be over- 
looked. 

The leakage loss in the average installation is always nearer 20 per 
cent than 10 per cent. Even concrete ducts do not prevent the leakage. 
In some large concrete ducts it is so great that pressure cannot be created 
in them. The inner surfaces of all air ducts, whether concrete or metal, 
should be liberally coated with a good paint. The larger duas of the sys- 
tem will have the most leakage, and should be painted while under pressure. 

Induced Draft 

TO decide upon satisfactory induced draft installation necessitates a great 
deal of experience and common sense. It is simple enough to figure the 
weight of the gases from the amount of air supplied to burn the fuel, and if 
the temperature is known, to figure the volume of those gases. The tem- 
perature, however, and consequently the volume, cannot be predetermined 
accurateh'. The inriltration through boiler settings, flue connections and 
economizer is an uncertain quantity'; it does not remain constant, but in 
time increases : the fan, however, must always be capable of overcoming 
an}' pressure set up in the fire-box. The infiltering air is cold and not 
only adds to the weight of the gases but reduces their temperature. An 
induced draft fan should be selected therefore with plentv* of reserve 
capacitN'. The driver for the fan should also be large, with at least 20 
per cent excess power. 

Table 17 ma}' be used as an example of induced draft fan sizes : but the 
dim.ensions differ considerably with different manufacturers. 

The chief troubles with induced draft fans are mechanical ; high speed 
fans, particularly, becoming unbalanced. The cinders passing through 
the fan cause a certain amount of erosion. The scroll sheet or round- 
about of the fan housing suffers most, and the inlet edges of the fan 
blades sometimes show signs of wear. In all induced draft fans the scroll 
sheet should be at least Vie-iru thick. When oil leakage occurs, dust 
and cinders are deposited on the blades. They pack down tight and form 
with the oil a heavj' hard cake. The leakage oil runs along the shaft 
through the shaft opening in the housing, and from there is carried into 
the fan wheel, covering the blades. 



M ECU A X T C A T. D R A F T 



237 




Table 1 7. Sizes and Weights of Induced Draft Fans. 









INCHES 






Boiler Output, 


Fan Outlet Area, 








Weight 
Complete, 


H. P 


Sq. Ft. 








Lb. 






A 


B 


c 




100 


1.6 


52 


48 


50 


1,000 


200 


3.2 


70 


64 


65 


2,000 


400 


6.4 


95 


87 


82 


3,700 


600 


9.6 


120 


110 


109 


5,500 


800 


13.00 


140 


128 


120 


7,000 


1,000 


15.00 


156 


143 


138 


9,000 


2,000 


32.00 


220 


202 


146 


17,000 


3.000 


48.00 


270 


248 


170 


25,000 



Most induced draft installations are of single inlet fans with overhung 
wheels. The two bearings are then outside of the flow of hot gases. This 
wheel is satisfactory, provided the shaft is large enough. 

The heat of the gases handled by the fan is conducted along the shaft 
to the bearings, and these bearings must be water-cooled. A short cast iron 
pedestal set in concrete is a satisfactory support. The concrete can often be 
brought up almost to the bearing bases ; the bearings are then mounted on 
I-beams securely embedded in the concrete. Built-up structural steel pedes- 
tals should be used only for very slow speeds and low powers. 

In the larger cities the nuisance caused by the discharge of solid 
matter from the stacks of power houses must be overcome. The under- 
feed stoker has to some degree eliminated the discharge of black clouds 
of smoke. But owing to the high draft pressures used at large boiler 
loads, the discharge of heavy cinders has been aggravated. In one type of 
draft fan, the dust and soot are separated from the gases, and are delivered 
into dust chambers, from which they fall by gravity into collecting hoppers. 
The cinder-separating induced draft fan has an efficienc}'- of dust removal 
of 75 per cent. It is substantially a paddle wheel fan of good propor- 
tions and takes about 10 per cent more power than the plain fan. 

The allowable speed on induced draft fans is considerably less than 
that on forced draft fans, even when the construction is identical. The 
temperatures of the gases handled by the induced draft fan range from 




Fifth Avenue Building, New York City, operating 1400 H. P. 
of Heine Standard Boilers. 



MECHANICAL DRAFT 



239 



300 to 750 deg. At lower boiler ratings with the gases passing through 
the economizer, temperatures may be as low as 300 deg. The flues are 
usually arranged so that the gases can be by-passed and do not pass through 
the economizer. With high boiler ratings and the economizer by-passed, 
temperatures will sometimes be as high as 750 deg. A high fan speed is 
then required, as the draft loss at these high ratings, even without the 
economizer, is considerable. In addition, owing to the high temperature, 
the fan must handle a large volume of gases. 

Somewhere between 500 and 700 deg., the elastic limit of iron and 
mild steel is only 50 per cent of the elastic limit at ordinary temperatures, 
say of 70 deg. The designers of rotating machinery have found that it 
is not safe to stress material above one-third the elastic limit. These con- 
siderations are borne out specifically by the behaviour of induced draft fans. 
The desire for high-speed direct-connected units resulted in many installa- 
tions of the backwardly curved blade fan for induced draft. This practice 
has been almost entirely discontinued, as the fans were installed for speeds 



40,000 



^30,000 






I Range of \ 

\ Induced Draft Jemperal-ures ] 




20,000 



"S 10,000 



UJ 



300 400 500 600 

Temperature , Degrees. 
Fig. 133. Variation of Yield Point with Temperature. 

that produce stresses of_ 10,000 lb. per sq. in., and they failed when the 
elastic limit of the materials was reduced because of the high temperatures. 
Fig. 133 shows how the elastic limit, or more properly the yield point, varies 
with the temperature. 

The peripheral speed of induced draft fans should be limited to 11,000 
ft. per min. It is true that most of the time when the gases are passing 
through the economizer a fan so limited w^ill be unnecessarily strong. But 
even though the high temperatures and large volumes occur only seldom the 
fan must always handle the necessary load. 

Load on Induced and Forced Draft Fans. The induced draft fan must 
take care of all the resistances, from the fire-box through the boiler and 
economizer. The resistance cannot be overcome by the forced draft fan, 
because positive pressures would be produced, blowing the gases of com- 
bustion out through the leaks. The forced draft fan has the advantage 
of working with gas of greater density, and should supply the pressure nec- 
essary to overcome the resistances as far as the top of the fuel bed. 

Suppose the density of the gases handled by the induced draft fan is 
half that of the air handled by the forced draft fan, a not unusual condi- 
tion ; then to overcome a given resistance the induced draft fan will require 
twice the power. Consider an installation in which 4 in. of water is 
required for the forced draft and a static suction of 2 in. of water is required 



240 M ]•: C 1 1 A X I C A L J; R A F T 



at the stack end of the ccoiioinizer. The difference between these two 
pressures (one ]>ositivc and the other negative) is 6 in. of water. Tf the 
forced draft fan snjjplied the wliole i)ressurc drop of 6 in. the horsepower 
required would he 

().0(J()158 X VoUunc X 6 

Fan Efficiency 

If, however, tlie wliole pressure drop was taken care of by the induced 

draft fan the volume handled would be twice as great and with the 

same fan efficiency the hf)rsepc;vver will be 

0.000158 X (2 X Forced Draft Volume) X 6 
Fan Efficiency 

=r 2 X Forced Draft Horsepower. 
The fundamental formula for the work done by a fan shows this differ- 
ence more clearly. The work done by a fan can be expressed by 

J = iuXQXli (10) 

where / is the work, zv the density, Q the volume, and It the head in feet 
(jf gas of density w. For both forced and induced draft fans the ])r(Kluct 
(7c; X Q), which equals the weight of gases, is the same, ignoring very slight 
change in si)ccil"ic gravity due to the different chemical composition of the 
two gases. Ikit h for the forced draft is only half the h required to produce 
the same difference in the water colunni when the work is don2 by the in- 
duced draft fan. The 6-in. water pressure represents 415 ft. of the cold air 
and 830 ft. of the hot air. In view of this peculiarity the induced draft fan 
should do only that work which on account of the nature of the service 
cannot be done by the forced draft fan. 

Testing of Induced Draft I-aiis. The greatest difficulty in testing these 
fans as installed is to locate a straight run of pipe where a steady, imiform 
and straight gas flow can be obtained. The i)itot tube, Fig. 131, gives some 
indication of the fan i)erformance. The volume of gasjs is sometimes 
determined from the weight of coal burned and the CO^ readings. Theo- 
retically the results should be fairly accurate, but practically they are uncer- 
tain, owing partly to the fact that ai small difference in the percentage of 
COj corresponds to a great difference in volume of the air. The densities 
of tlic hot gases of combustion and of the cold infdtering air differ greatly, 
so that the mixture stratifies, and it is extremely difficult to secure a fair 
sami)lc. The leakage is through the walls of the passages; consequently the 
air almost entirely surrounds the moving mass of gas and the percentage 
of COa will be greatest near the center. Even after passing through the 
fail this stratification is still evident. 

The most satisfactory method of testing an induced draft fan is to 
divide the fan inlet duct into say 16 equal areas and take a reading of 
velocity with the pitot tube at the center of each of these areas. Knowing 
the tcm])eraturc and consequently the gas density, the volume of the gases 
can be calculated from these readings. The formulas for the testing of 
forced draft fans are applicaljJe. Tlie velocity sliould be measured on the 
inlet, ratlier than the outlet side. The llow to the inlet is almost invariably 
accom])anied by an increase in velocity, and is a maximmn at the fan inlet. 
The movement of the gases tends then to become steady and uniform, and 
the velocity can be measured accurately in a short run of straight Hue. 

On the outlet side the fan wheel causes local eddies in the air, so that 
any velocity determination is extremely difficult. The test must be made 
with the pitot tube or its close equivalent. 

Tn the smaller plants the induced draft fan may furnish all the neces- 
sary draft, the stack being only a short connection to discharge the hot gases 
above tlie r(M)f. This is good practice from the standpoint of cost but a 
plant of any si/c may create a nuisance, as the discharged soot and cinders 
settle thickly on nearby structures. Most of the larger plants use fair sized 



M I', (■ II A X I C.\ I 



) K A I' 'V 



241 



stacks and when operating at low rating hy-i)ass iho indnccd drafl l;iii. 
Two dampers arc then rccpiircd ; one on the fan inlet and llie other in llie 
by-pa.ss ; the second damper separates the suction and discharge ol llic 
fan. Tlic fan damper shonhl be on the inlet rather than on the onllet side, 
because the dead pockets formed by a fan with an outlet damper shotdd 
he avoided in induced draft (lues. VVhen Ihe fan is by-passed and tlie outlet 
damper closed, there is no movement of gas in the whole fan housing. 
Such an arrangement has been known to result in an explosion. The 
damper in the by-j)ass shoidd be as tight as possible. The pressure difference 
between fan outlet and iidet is equal to the full static pressure developed 




Fig. 1.54. Ideal Connection ol Fan to Stack. 



by the fan and any leakage space around the by-pass damper will permit a 
recircidation of gas, which will reduce the capacity of the fan for liandliMg 
fresh products of conibuslion from the boiler. 

In laying out the connection from the fan ontlet to llie stack port all 
bends (sharp ones especially) should be avoided. The static pressure in 
this connecting duct is ])elow atmosphere only by the amount of suction 
produced by the stack. When air Hows around bends the pressure is 
greater on the outside of the cnrve. If a pressure around a bend becomes 
greater than tiie stack suction, some of the products of combustion leak 
into the I)oiIer roon). Iwcn a very small anionnt of this leakage is objec- 
tionable, as it makes the boiler honse unpleasant to woik in. JM'g. 134 shows 
an ideal connection between fan and stack. 



243 



CHAPTER 8 



PIPING AND ACCESSORIES 

THE same care given to the design and installation of boilers and engines 
should be given to the piping system. The object of any system of boiler 
room piping is to conduct a fluid safely from one point to another. This 
must be done with economy, but no commercial consideration should be 
allowed to interfere with the fundamental requirement of safety. More 
accidents originate in defective piping than in defective boilers. The failure 
of pipe, fittings and valves is due not as a rule to excessive fluid pressure, 
but to the presence of water in steam lines, excessive and continued vibra- 
tion, changes of temperature, and faulty methods of support. 

Wafer in steam lines is a source of danger, and every precaution should 
be taken to avoid its presence. 

The chief danger from water in steam lines is water-hammer, which 
generally results from admitting high pressure steam into a cold pipe con- 
taining condensed water. In pipes nearly horizontal, Stromeyer has shown 
that under these conditions a slug of water may attain sufficient velocity 
to burst massive fittings. He cites an instance where a large boiler stop 
valve disk was turned inside out and driven into the boiler against the steam 
pressure. Piping systems should be designed either to avoid the possibility 
of water accumulating on top of closed valves or to provide ample and 
accessible drainage facilities. This requirement is of especial importance in 
connecting boilers into a main steam line. Where pipes are connected to 
safety valves to enable them to discharge above the roof, the connection to 
the safety valve casing should be by means of a Tee. A pipe — at least V/i 
in. — should be taken from a blank flange on the lower leg of the Tee to 
insure permanent drainage ; and this pipe should be without a valve or other 
obstruction, but should discharge into the atmosphere or blow-off tank. 

Piping should be erected so that water-collecting traps or pockets will 
not be formed. Large drain pipes should be provided wherever pockets 
cannot be avoided. Drains should be placed at the bases of risers and wher- 
ever water can accumulate because of the closing of a stop valve. If drain 
valves are not likely to be attended properly, drains should be trapped, so 
that the water will be removed automatically. Steam supply branches should be 
connected to the upper side of mains. Drains should be connected to the low- 
est point of reducing flanges, reducing tees, and taper reducers. Steam lines 
should be installed with a uniform grade of about 1 in. to 40 ft., so that 
they will drain to some predetermined point. Drainage is more complete if 
the water and steam flow in the same direction. 

Vibration In piping is a source of trouble and danger to the pipe itself, 
and to joints, valves, fittings, supports and anchors. It is often set up by 
water slugs delivered by ill-designed or carelessly operated boilers, or from 
accumulations of condensed water, Alodern power plant practice favors 
high steam velocities, which tend to diminish condensation. But slugs of 
water are then driven along at higher velocities, and as their kinetic energ\' 
increases as the square of their velocity, the vibration trouble is aggravated. 
Consequently, drainage facilities cannot be neglected because of high velocity 
alone. As a matter of fact, condensate is more apt to be carried past drip- 
pockets and separators by high, than by low velocity. Vibration is also 
caused by the intermittent flow of steam to reciprocating engines, unless 
separators or receivers are installed in the steam lines close to the engmes. 



244 



PIPING 



Expansion and Contraction. Pipes are bound to expand when heated 
by the entermg steam and hot water and to contract as the temperature falls 
with the shutting off of the steam or water. The increase in the circum- 
ference of a pipe because of an increase in its temperature is of little practical 
consequence. The lengthwise (linear) expansion of a pipe is great, how- 
ever, for pipes used in power plant practice. The force exerted by expand- 
ing and contracting pipe is practically irresistible. Therefore, piping moist be 
anchored, and then the direction in which it will expand and contract can be 
predetermined and the expansion and contraction absorbed, so that it will not 
damage the pipe itself, the fittings forming a part of the line, or the appara- 
tus to which the pipe is connected. 

Selection of System. The selection of the piping system should be based 
upon the factors of uninterrupted service, low cost of operation, and low 
cost of installation. The piping system, boiler and prime movers should 
be selected at the same time, and to form a single unit. If uninterrupted 
plant operation is of value, piping must be so designed that its failure in 
part will not shut down the whole plant. The point to which it is justifiable 
to carry refinements insuring continuous plant operation depends upon the 
commercial value of uninterrupted service. 

The layout of essential power plant piping should be consistent. If 
steam mains are well protected, feed mains, exhaust mains, oil lines, and 
other essential portions of the piping equipment should be protected in the 
same way. Heater, economizer or condenser connections need not be thus 
refined, because operation without them is possible, although it may be 
decidedly undesirable. This is especially true of plants containing more 
than one of each economic auxiliary. These should be connected so that 
they can be operated temporarily at an overload with reduced economy, 
should one unit or its connections fail. The feed-water temperature may 
be 150 deg. when two heaters are used instead of three, but even that is 
preferable to cold water. Overloaded condensers may mean a vacuum much 
less than normal, but this is preferable to exhausting to atmosphere. 



Ji 



'-Exhausf Marin • , 



Engim 




Engine 



--Condenser 






"T r 



Boilers 



Heater-' 



F 



^■"- Sieam Main ^^Eeed Main 

Fig. 13 5. Diagram of End to End Single Header System. 



The single header system. Figs. 135 and 136, is simple and the first cost is 
low. For the end-to-end arrangement of boiler room and engine room. 
Fig. 135, this system is not reliable, as a break in one of the mains shuts down 
the entire plant. For the back-to-back arrangement of boiler room and 
engine room, Fig. 136, the feed-water header and exhaust header are still 
undesirable, although the steam header can be divided by valves and part of 
the plant operated if some one section fails. 



PIPING 



245 




Fig. 136. Diagram of Back to Back Single Header System. 

With the duplicate header system, Figs. 137 and 138, the plant is much 
more reliable, but the first cost of the system is high, and each piece of 
apparatus must be connected to two independent headers. Unless both 
headers are in continuous operation, or are located at a considerable distance 
from the apparatus, joints and connections are subjected to severe strains 
due to expansion and contraction. 



■^ 



-rExhausf Main 



T 



Englnz 



Engim 



3^ 



i^-'Condznser 



fnginz ■ — ■ y 



^ 
S 



Heoit'er 



y Feed Pumps 



Boilzrs 



m. 



TT 
Feed Main^' 

^^^ 



Ei 



£ 



:ii:| 



^"'"-Sizaim Main 
Fig. 137. Diagram of Duplicate Header System. 



:r 




o 
vo 

(U 



CO 

>> 

G 

a 

5 CO 

O i- 
u 

CO 

CO 
^W 

(U -S 
-^^ 



o 
U 

*s 

ID 

(4 

u 

«{ 
bO 

'cO 

Ui 
(U 
T) 
(U 

(I4 



PIPING 



247 



Ua- 

m 

& 



>feec^ Pumps 



Boilzrs 



iSfLd 



^-fizatzr 



H 



Ed 



H 



Mains 



Engine 






ti: 



E£:f 



Engine 



\5feam 
Mains 



Enginz 



r'Conofenser 



■r 



^-Exhausf Mains 



Fig. 138. Diagram of Duplicate Header System. 

The ]oop or ring header system, Figs. 139 and 140, is more reliable than 
the single header system, but its first cost is high. It has advantages when 
the physical limitations of property or buildings prevent the installation of 
a unit system. 



";^Exiiausf Loop 
-^ r^— I ri 



Engim 



T r 



Engine 



T- r 



Engine ^-Condenser 



Heater- 






^Feeol Pumps 



Boilers 



^^Z 



-i^ 



~ 



i 



^y-- steam Loop 



Feed Water Loop-^- 



Fig. 139. Diagram of Loop Header System. 

The unit system, Fig. 141, represents ihe l)est standard practice for large 
plants, but it can well be used in plants of moderate size. The complete 
plant is virtually composed of small independent units, any one of which 
can be shut down without affecting the others. The first cost of this sys- 
tem is high, but is more than justified when uninterrupted service must be 
had. The high first cost is due not alone to the piping system but also to the 
fact that each engine or turbine has its own separate boilers, condensers, feed 
pumps, circulating pumps, vacuum pumps, and feed-water heaters. Separate 
coal-and-ash handling equipment is also supplied for large units. 



248 



frf 



PIPING 



._. rzsoi F'jrrps 



Boilers 






V 



7l 

Heater^ 



is 



^ 



ii 



jI 



Lj. 



i 



L-i 



'zzy i',^~z' 



oreotm uoop^' 



h-l pi-| hI i^ i4 .^ 




Englm 



r]^ 





^-f.'-rj-^r _::jc-x 



Condenser- -■** 



Fig. 140. Diagram of Loop Header System. 



Engine 






Condenser^ R r 



4- 



t"4 



I 



l-J 



Enginz 



I 



Engine 



bl 



4i 






,>>5r?:».?7 /" ."22:7 ',;'yrz: 



•R^ 



^ _ .-reoTTsr 

ZWafer ;.- ^^ ^ 



"5 



"H 



3 



c: 



-l- 



4- 



U 



•^^ 



^ 









,^,-223 .-.yz' 



1 



Sir? -iJ 



Condenser ^ 



H 



^ 



-ec/rer I 



"H 



■^ 



Fig. 141. Diagram of Unit System. 



PIPING 



249 



In a modified unit system, Fig. 142, the complete plant is divided into 
distinct sections, each entirely independent of the others and operated as a 
complete plant. This system is not so reliable as the unit system because 
sections of the same mains must be used ; fewer auxiliaries however are 
required. It is not desirable for plants which operate at a high load factor, 
but is adapted to those whose daily light load period is long enough so that 
the mains can be repaired. The number of the sections into which the plant 
is divided depends upon the load characteristic. If a plant requires two- 
thirds of its capacity for its lightest load, three sections would be necessary. 
A plant operated at half load for the greater part of each day could be 
divided into two sections. 



Condenser ^^^ 




~/iecif(zr 



Boilers 



Cono/enser—' 

Fig. 142. Diagram of Divided or Sectional System. 



The modified unit system, Fig. 142, actually requires but two auxiliaries 
of each kind ; each set of auxiliaries hov*^ever should be able to handle the 
light load for the entire plant. If the capacity of each set is sufficient_ for 
full load, even though it is overloaded, the danger of shutdown due to failure 
of mains or connections is greatly reduced. A complete set of auxiliaries 
for each section of the plant adds materially to its flexibility, economy, and 
reliability. In deciding upon the number of sections, the size and accessi- 
bility of the mains and the time required for their repairs should be con- 
sidered. 

Piping should always be accessible, for safety and economy. The ac- 
cessibility possible for any given set of physical conditions should be a factor 
in the selection of a piping system, because it affects the time required for 
repairs and therefore the reliability of plant operation. 



2S0 




A part of the 8550 H. P. installation of Heine Standard Boilers and Heine 

Superheaters in the New York Central Railroad Terminal, New York City. 

This company operates 18,000 H. P. of Heine Boilers. 



PIPING 251 



The durability of boiler room piping has an important effect on the 
continuity of service. Irrespective of its first cost, the best pipe and pipe- 
fitting material, will be the cheapest in the long run, for any but the most 
temporary installations. 

A diagramatic layout of boiler room and engine room piping should be 
made for every plant, and a copy of this diagram posted in a conspicuous 
and accessible place in both boiler and engine room. The diagram should 
be large enough so that all the lines and captions can be quickly distin- 
guished. All valves should be numbered and the diagram accompanied by a 
tabulation of the lines or equipment controlled by each valve. The diagram 
can well be made as a tracing. Any requisite number of copies can then be 
made, and it can be easily corrected and kept up to date in the event of 
changes in, or additions to, the piping system. 

Identification of Piping 

A STANDARDIZED color scheme is a practical aid to the identification of 
-^*- piping. The report of the A. S. M. E. Committee on Identification of 
Power House Piping, suggests that color shall be used on flanges, valves and 
fittings only, the piping itself being painted to conform to the color scheme 
of the room. The colors recommended are as follows : 

Division Color 

Steam — 

High pressure White 

Exhaust system Buff 

Water — 

Fresh water, low pressure Blue 

Fresh water, high pressure in boiler feed lines Blue and White 

Salt water Green 

Oil, delivery and discharge Brass or Bronze Yellow 

Pneumatic Gray 

Gas — 

City lighting service Aluminum 

Gas engine service - Black, red flanges 

Fuel Oil Black 

Refrigerating — 

Pipe Gray 

Flanges and fittings White and Green Stripes 

Pipe and Piping Materials 

"Practically all boiler room piping is made of either mild steel or 
-*- wrought iron. Because of its lower price, steel pipe is more common 
than wrought iron, and for most purposes fulfills all requirements. 

Wrought Iron pipe is more durable than steel pipe, especially when buried 
under ground or subjected to extreme exposure. It is said not to corrode as 
easily as steel and therefore is to be preferred for blow-off pipes, drips and 
drains, and wherever corrosion may be severe. The term "wrought iron 
pipe" is often used loosely, for both steel and wrought iron pipe. In the trade 
steel pipe is furnished, unless genuine wrought iron pipe is specified. 

Cast iron pipe is used for low pressure work. Because of its low tensile 
strength and consequent great weight, it is seldom used for high pressure 
pipe. Cast iron is used however in the construction of headers, although 
it is not recommended for high temperatures. For complicated headers with 
a number of branch lines, a casting is cheaper than fittings, and the number 
of joints is considerably less. 



252 



P T P T X G 



Cast steel is used for headers, especially for highly superheated steam, 
and resists high temperatures much better than cast iron. The cost of cast 
steel is high, and it is difficult to secure uniform castings, free from hidden 
defects. 

Brass withstands the corrosive action of hot water better than iron or 
steel, and is sometimes used for feed-water lines and headers. Its high cost 
limits its use even for this service and practicalh^ prohibits its use in other 
parts of a piping system. It is weak and brittle at high temperatures. 

Copper is expensive, deteriorates rapidly under high temperatures, and 
weakens under recurrent stress variations. It was formerly popular in marine 
service because of its flexibility, although this is offset by its low tensile 
strength. 

The use of high pressures and high degrees of superheat is increasing, 
so that the total temperature of water and steam must be considered in se- 
lecting materials. Table 18 gives the average tensile strength of metals 
at different temperatures, as determined by the Crane Company. The table 
ypplies to the initial effect of high temperatures, but does not indicate the 
effect of continued high temperature, as the time each specimen was heated 
had to be limited. The results show however that cast iron undergoes a 
slow but constant loss of strength when subjected to temperatures over 400 
deg., and that steel does not undergo any material decrease, other than its 
initial loss of strength, because of continued temperatures as high as 800 
degrees. 

Table 18. Effect of Temperature on the Tensile Strength of Metals. 



Material 


AVERAGE TENSILE STRENGTH, LB. PER SQ. IN. AT 
TEMPERATURE NOTED 




70 


300 


450 


600 


750 


900 


950 


1000 


1030 


Steam metal 


31,780 
35,345 
34,170 


26,370 
34,260 
36,025 


21,900 
27,630 
33,050 


12,180 
16,100 
21,380 


10,280 
13,000 
19,640 


9,530 


6,630 
9,650 






Special brass 

Navy "G" bronze. 


6,400 




Hard metal 

Cast Monel metal. 


33,735 
52,870 
22.060 


34,280 
23,260 


31,180 
47,200 
20,730 


23,150 
39,450 
21.240 


19,170 
41,787 
21.925 




10,825 


5,710 


26,400 


Soft cast iron . . . 






19,820 














Ferro steel 

Malleable iron 

Cast steel 


32,692 
37,625 
73,325 


33,290 
33,505 
76,570 


33,400 
33,280 
81,167 


33,110 
34,000 
67,366 


32,860 
34,055 
41,388 


25,780 


' 27,ii6 


27,310 
■ 17,568 













Commercial wrought iron and steel pipe is divided into four weight 
classifications; standard, extra heavy, double extra heavy and large O.D. 
A fifth classification, lighter than standard pipe and known as "merchants 
pipe," was formerly made but its use has generalh" been discontinued. 

Standard, extra heavy and double extra heavy commercial iron pipe is 
designated by its nominal internal diameter, in sizes from Jg to 12 inches. 
The external diameter of extra heavy and double extra heavy pipe is the 
same as that of standard pipe, and the internal diameter therefore is smaller. 
Above the 12-in. size, pipe is usually classed as "large O.D." and is desig- 
nated by its actual outside diameter, although some manufacturers list sizes 
with nominal internal diameters of 13, 14 and 15 inches. 

Commercial wrought iron and steel pipe is butt-welded in sizes 1^ in. 
or less for wrought iron, and 3 in. or smaller for steel. The larger sizes are 
lap-welded. 

The principal dimensions and the weight of standard wrought iron and 
steel pipe are given in Table 19. 

The same data for extra heavy and double extra heavy pipe are given 
in Table 20 and 21, respectively. 



PIPING 



253 



(L) 
ft 



CO m 



m 



A 
^ 



cc 



a 



c 

CO 

ft 

a 

o 
U 



T) 




CO 






H 


n 


,»^ 




m 







6 
S 


4-1 

CO 
2 



Water in. 

One Ln. 

Ft. of 

Pipe 


lO lO 05 


(M>-iin 

CO CO t- 
i-H (N CO 


OOCO Ift 
i^OO lO 
«D 00 -^ 


CO in CO 

C-O 00 
OC<l(N 


05 CO CO 
rH rH t- 

ino5 CD 


•^ CO 05 
(N05t> 
mOrH 


t-ooco 

00 I-H CO 

CO(NC0 


O-i^CD 
00 00 OS 

OS rH rH 


t-05m 

CD(Nt- 

t-ot- 


00(NO5 

CO OOO 
rH I-H m 


CD 00 
rHC- 

miN 


^o' ■ 




tH 


(Ncotj* 


lOCDOO 


IN CO IN 

rHrHIN 


rH t- m 

(NINCO 


■^ Tf rH 

CO CO -^ 


05 CS OS 

T* -^m 


OS 05 05 
cot- 00 


o m 

OIN 

I-H rH 


U.S.Gals. 
in One 
Lin. Ft. 
of Pipe 


CO lOO 
•OO'-i 
rtOOO 


(X) 00 iC 

ooo 


OOCD -^ 

t- o t~ 

Oi-i 1-1 


05^^ 
Tl<00 1-1 

(N CO in 


rHOOOS 

CDINCO 
CD ooo 


rHINOO 

o rH m 
mocD 


(35 IN 00 
O5CDC0 

m(NiN 


IN cot- 
OS (OS CO 

rH005 


'*meo 

CDt-CD 
OS OOrH 


m 05 CD 

00 00 IN 
(N'*t- 


m(N 

'*rH 
OO 


Oo ■ 








■ "rH 


rHININ 


(NC0t1< 


'*'*'* 


mmt- 


00 050 


(Mm 

1— 1 I-H 


Length 

to 
Contain 

One 
Cu. Ft. 


. t-t-co 


CD -^ 00 

OC0.-H 

050CD 


mco CO 

t- CO I-l 
IN t>05 


c-05in 

t> t~cO 

o -^ in 


cgOGO 

rHCOOS 
COOrH 


-.^t-m 

00 rH I-H 
05000 


00 -^ m 

t-05CD 
OOlNt- 


m CD m 

OOIN rH 

t-00 m 


•^ CO '* 
m t- ■* 

(NINO 


cooot- 
000 05 

OSt-CD 


<-l 00 
(NOS 
CD 't 


&j coco -^ 
"co x)io 

(N 1-1 


COOCD 

t- t> ;d 


«DO(N 
05 1:-^* 


OC5T)< 
CO 1-H rH 


1-1 05t- 
rH 


-*COIN 


IN IN rH 


rH rH rH 


i-lj-ii-t 


o 


1 
1 


0) 

P-i o 
o . 

h- 1 


0) 

o 

H-l 3 


O5C0 t- 


,-1 LOl-l 

,:j<CO^ 


t-(N t- 

CD t> -^ 

t-cooo 


t- in CD 
in (NO 


00 t- CD 

T}< -"^ in 

05 00 


OS CO CO 
(N-<*t- 

cD m ^ 


OOt-TT 
t-INt- 

Tf T* CO 


CD rH t- 
C- 00 -rj* 
CO CO CO 


moo 00 

rH rH 00 
CO CO IN 


ooo m 
CD m CO 

IN(N(N 


IN OS 
(NOS 
IN y-H 




5£) -^CO 


COIN 1-1 


rH 1-1 rH 


o 














01 


i-ieO 00 
•COt-lrt 


^coo 

lOCD 05 


1-lOM 
Oi-iO 

coocn 


OOrHTt 

(N OS in 

ecocn 


00 coco 

^CDOO 

oot-co 


CDOIN 
OO'* 

m m-5j< 


IN com 
'cftosm 

Tf CO CO 


mm m 
mmiN 

CO CO CO 


0S05(N 
05 05t- 
(N(MIN 


^00 '* 

mco(N 

(N(N(N 


INO 

rH05 
(NrH 


0>t-U5 


■^COIN 


(NINr-l 


1-H rHO 
















0) 

1.1 
< 

M 

b< 

> 

c 






oco'^ 
in CO 05 

(MCOt)< 


OS 05 in 

«3 05C- 

tot-o 


^OOO 
O(M00 
IXMCD 


^ ooo 
c-ooo 

rH CD CO 


rH CD m 

00 IN CD 

mo5(N 


05^*00 
OS t- t- 
COOSrH 


(NOOrH 

t-oo 

O OS -^ 


CD OS IN 

t-t-m 

oomo 


OOOrf 

COOO 
iN'*m 


COCO 
ot- 

CDrH 


Co 
t/2 




rH 


rHININ 


CO CO "^ 


mcot- 


00 05 05 


OrHCO 
rH rH rH 


IN-* CO 
r-ir-tr-i 


t-ooo 

rHrHIN 


(Nm 

IN IN 




t- -^ tH 

^lOOOi 
^Oi-Ht-h 


■<:f CO ''^f 
OCO'^D 

coiooo 


in«5 in 
Oicoin 
^ooo 


00 CO CD 

00 OS 00 
c-cooo 


Ot~CD 

CO -^ o 

C-050 


rH 00 rH 
05C0 CD 
OOOrH 


t- com 

IN 00 00 

oc-m 


osmco 
CO ooo 


O t-CD 

005 00 
OOOOO 


m '* CO 
oomt- 

'*CO'* 


CD CO 
COOO 
00 05 






I-H (N CO 


"* t- 05 


iNino 

rHrHIN 


00 00 rH 

IN CO m 


0(NrH 

mcDoo 


ooom 

00t-O5 


'*C0 t- 
rH rH CO 
rH 1-H rH 


05 (N CO 

mooo 

rHrHIN 


rHOO 
COOO 
(N(N 


(D-j 
X C 


05 05 00 
^i-HINCO 


ttCO 00 

in com 
loooco 


■^ ino 
to CO CO 

I-H 00 Tj" 


(NrHCD 
05INCD 

^ CO in 


TjH inco 
ocoo 

05CDC0 


IN'* CO 
t-CO(N 

■* CD •* 


cooco 

(NCOCO 

^t-t- 


CO CO "^ 

CO CD CO 

t- 1--<* 


CO COOO 

t- t-co 

COCO<J5 


miNO 

rHCDOO 
t-OOS 


OSC3S 

com 

•^rH 


GO 


T-l 


ININ '^ 


CD05(N 
r-l 


in OS'* 

rHrH(N 


•^ moo 
CO ■* m 


OOINO 

mt-<35 


OOOO 

05 0SO 


t- t-co 
(M(Nm 

rH rH rH 


COr-ICD 
t-0(NI 
rH(N(N 


Tj<-* 
mrH 
(NCO 


« 

ci 
m 

0) 

s 

3 
« 
1.1 

• 1-4 

o 


CI « 

h- 1 


10-^05 
•OOi-llO 


10 00 05 
05 10CQ 


inoo -^ 
coino5 
coo -^ 


t~ 00 CD 

inco -^ 

C- CD I-l 


00 CD CD 

•* inin 

CO rH 00 


^COCD 

m CO m 

OOCO 


CO OS OS 

t- 00 rH 

OOO 


CO OS 00 
■rj" t- m 
00 -rfm 


IN (35 CO 
00 OS IN 
OS CD CD 


00 05 00 

cooco 

t-05 05 


05(N 
t-co 
OS IN 


t-IOl-HrH 


tHM CO 


•^in ix> 


t-05rH 

rH 


iN^in 


05(Nm 

rH IN (N 


moo IN 

IN IN CO 


rH rH T* 

CO CO CO 


C~-t- rH 

CO CO "^ 


^t-o 
-* '* m 


COO 
mcD 




(M^i-I 
t-05N 


05 05>-l 
CO O5C0 


in 05 T-H 

i-h;0 t£> 
(N05-<^ 


IN CD CD 

CO OS CD 

o OS in 


t-oot~ 

cooc- 

rH t- ^ 


CO m CD 

rH m OS 
00 05O 


CO00(N 
O5C0t- 
OIN t- 


INlNTt" 
t- t- rH 
t-t-OS 


m m IN 

m m 00 

0005 


-* m c- 

(NCOO 

rH IN '* 


(3s IN 

rJ<CO 

moo 


l-li-lt-IC^l 


<NCO'* 


inint- 


050IN 

r-< rH 


•^ in t- 

rH I-H rH 


ocot- 

IN(N(N 


t-oco 

(NCOCO 


COCO CO 
CO CO CO 


ooco 
'*'*^ 


t-oco 
'*mm 


CD IN 

mco 




CO 

O c 3 

>- M O 


lO ICOO 


in CO 00 

00 i-l<£> 


i-H I-H 00 

00 CO t- 

INt-O 


05C0<N 
1-H rH O 
00 COC<l 


05(NO 
OOT^rH 
00 CO 00 


m 050 

00 CO o 

1-Ht-O 


OS ooo 

OOOO 

00 rHO 


0(N t- 

ocOTi< 

OrH(N 


O CD '* 
OOOJ 
Ot-OO 


mo(M 
t-oo 
com CO 


(N t- 

00 rH 
^CD 


h^lo 


rH,-l 


(NC<!eO 


lOt-OS 


OlNTf 


OS com 

rH(N(N 


ooti<(n 

(NCOCO 


m rH CD 

CO'*'* 


mom 


0'*(N 

cocot- 


005 
OOOO 




Tf -"^ t- 


OOOO 

incot> 

00.-l«> 


IN t~IN 

C^ rH in 
IN t-«5 


CO in 05 

05t-0 
t- in rH 


ooot- 

O5C0rH 

t> incD 


1* '* CD 
t- -^ OS 

05 m CO 


-<* t- rH 

moo 
mo5(N 


ocot- 
T* oom 
(N^m 


CO IN 00 
t-co CO 

t- m m 


co OS Tji 
t-t-o 
m m t- 


ot- 

Tjtt- 

oom 


,-?o 


r-t I-H 


(NINCO 


int-05 


0(NTf 

rH rH rH 


OOCO'* 

rH(NIN 


00 CO rH 
(N CO CO 


Ti<om 
CO 1* '* 


CO OS Tf 
'* T* m 


00 IN (35 

mcocD 


com 

t-00 




t-OOOO 




I-H 1-H 1-H 
I-H tH 1-H 


00 00 00 


00 00 00 


00 00 00 


00 OOOO 


00 00 00 


OOOO 00 


OOOO 00 


00 00 


1 
Eh " 


oooot-i 

•50 00 05 

Cooo 


05 CO CO 

o --leo 

1-1 ,-( I-H 


oin^ 
Ti< •>* in 

i-HrH rH 


CO CD CD 

OrHIN 

(NININ 


t- t>00 

CO '* in 

(N(N(N 


O rH t- 
OOOt- 

(NCO(N 


(NCg05 
(N^t- 
COCOIN 


t- m m 

OCDt- 

CO CO CO 


omm 
cot-t- 

CO CO CO 


m mco 

t-t-C5 

CO CO CO 


OS OS 
OO 

'* ■* 


o 






















6 
ca 






05 -i^J^ CO 

<Ci«3 05 

•(MCOTf 


N -^05 
INN 'S' 
(£> ooo 


oo t- 

OOi-HO 

co;do 


OS 00 00 
CD CO Tf 

■<s" o in 


CO COO 
INOr)< 

oino 


mcO rH 
CD(NC~ 
OOO 


rHrH(N 
00^05 
0S05rH 


cooo 

COINO 

rHOO 


ooo 
oso m 

OOIN 


oo-* 
m m I-H 

(N(N(N 


CO(N 

OOOO 
r-l I-H 


H-(0 


I-l 


I-H rH OJ 


(NCOCO 


Tt<-«i<in 


cot- 00 


t-ooo 


OOrH 


IN IN CO 


'*mcD 

rH I-H rH 


t- OS 

1-1 rH 


^ Cg 
X! C 


in o lo 
o -^ c- 


OOIO 

-* lO 1-H 

oooco 


ooin 
coot- 

<X> 05C0 


inoo 
t>oo 
ooino 


ooco 

OOCD 

mom 


mm m 

(N(N(N 

CO CD CO 


mm o 
(N(Nm 

CD CD t- 


OOO 

m m m 
c-t- t- 


ooo 
mmo 
t-t-o 


OOO 

ooo 

OOO 


OO 
OO 

OO 


►-HO 


iH r-* 


rHrHIN 


(NCO-^ 


Tj mm 


CDt-00 


00 050 

I-H 


OOrH 
r-< T-< r-< 


ININ^ 

I-H rH rH 


mcDt- 

rH rH I-H 


ooo 

rH(N 






:^:^;^ 




I-H rH (N 


(NCOCO 


Tj< -rt" m 


CO t-00 


00 050 


OOrH 
1-1 rl r-l 


(NINCO 


Q 
d 

T^m t- 


QQ 
do 

ooo 

rH(M 




Penn Mutual Life Insurance Building, Philadelphia, Pa., equipped with 

Heine Standard Boilers. 



PIPING 



255 



a; 

a 

>> 
> 

V 
CO ^ 

■^ a\ 
W . 

O G 

. . rt 

a 

a 

o 

c d 

CO j_, 






Si CO 



o 

csi 



43 

CO 

H 



be -J 



o. o 



J= 3 



h4S. 



0) 
C/1 



w 



S S c =" 



aiJS 

04 a 
a>M 



^ CO 

-C C 
Eh 



OO O On 
On On 00 



fe 



SO O '^ 

On O O 
ro CN ■<— I 



O 00 O 
NO -rfi ro 
• t^ NO O 



'l>- CS Ov 



•<— I PO 00 
rO !>• lO 

;^ O NO 



ON t^ lO 



. ro t— t^ 

COn lO T-H 



= 0-^ 



0*0 
C/3 



On On 00 



CO 
72 



lO On ON 
t^ -^ fN 
.NO ON ro 



CN NO ■«-i 
r^ ON CN 

jjCN NO '-H 



■^ lO 00 
. T-H ro fO 

J . . . 

o 



«0 On NO 
• On '-H (M 
C o '-^ '— I 



lO r^l ro 

T-H o rsi 



lO O ID 

O rtH^ 
Th LO vO 



>-i\i-i\«i 



t^ NO CO 

^— I ^— I On 
O O T-^ 



lO CO O 
^ CO O 
NO CO CN 



lO !>• '— I 

On rfi On 
On ■'-H On 



t^ t^ -rti 
■^ CO O 

LO NO On 



'^ CO CN 



O CO 0\ 
CN CO CO 

CO T^l NO 



^ CO On 
CO CO tH 



tJ< NO 00 

lO NO LO 

lO 00 CO 



to '-H t^ 

•^ CO O 
t^ CO o 



On ON •>— I 
CO On CO 
NO r^l T-H 



r<i CO •rfi 



t^ CO ■•— < 
00 t^ ^~ 

O Ttl T-H 



t^ T* On 

T^ to f^ 



NO rg t^ 
to r^ On 



O O lO 
00 O CO 



O t— NO 

ID 00 NO 
rs -^ r^ 



(M T-H 00 

T-H 00 Tt 



00 NO On 

00 Tt< NO 
On to On 



T-H O 00 
O T-H O 

CO O NO 



T-H 00 1>- 

00 NO !>. 

00 o -^ 



CO t^ CO 
00 NO lO 
CN t^ ON 



•^ to o 
NO CO CO 
T-H CO •^ 



CN CN -^ 



lO CN CN 

T-H T-H On 



T* t:^ NO 



to On T-H 
T-H vO NO 
r<l On ^ 



NO T-H fN 

On CO CN 
ON NO O 



■^ O OO 
OnO -^ 
T-H (M CN 



00 O On 
t^ O CO 

CN to On 



T-H T-H O 



o o to 

NO O t-^ 
NO On CO 



T-H T-H fV) 



NO T-H CN 

r^ O O 
On 00 CN 



CO T-H NO 

CO CN T-H 



><**-- to 

Ttl T-H CO 
NO CO T-H 



00 T-H ^ 
CN On lO 

CO O On 



T-H T-H O 



■^ NO 00 

to T-H r^ 

CN O NO 



00 to 00 
CO O 00 

C^^ NO 00 



"* NO 00 



CN T-H NO 

On CN NO 
^ NO to 



NO On rs 



00 T-H 00 

On T-H NO 
CN T-H to 



t^ On O 



On O CN 



T-H CN to 

NO lo o 

NO CN to 



t^ O CN 



CO O "^ 

CN O NO 
CO ON CO 



lO O O 

r-~ O O 
00 to O 



CN CO Tfi 



lO CN to 

CN NO T-H 

to On ON 



00 O CO 
O On On 
On 00 1>- 
O • • 



00 CO NO 
Th NO 00 
00 t^ NO 



t^ O CN 

O 00 T-H 
■^ T-H T-H 



rfi to NO 



t^ to -^ 

On »0 On 
Tt ^ ^ 



■^ 00 



^ to NO 
O CO O 
On NO CO 



to On -^ 



Ot^ o 

CN t^ CN 

O ^ r-H 



t^ 00 1^ 

CO OJ>- 

T-H !>. -^ 



TtH tot— 



CO T-H 00 
00 T-H t^ 

On NO t^ 



•<* t^ o 

T-H T-H CN 



X>- lO to 
CO ID f^ 

CO CO CO 



CO -rti T* 



O OCO 
O O NO 
lO o to 



T* 'tl to 



■^ t^ T^l 

CN t^ to 

to T-H T-H 



to -^ CO 



CO NO O 

NOf^ O 

NO to to 



NO O CN 

t-- o ^ 

to lO T* 



lO CN CO 

OON NO 

■^ T-H t-- 



t^ CN CO 

NO t^ NO 
O^ NO 



NO T* to 

r<i CO '* 



CN '^ NO 

r^ nO CN 

T^ NO ^ 



^ to 00 
CO -^ to 



On CO to 

On T-H to 
O 00 On 



00 O CO 
T-H CN CN 



CO to NO 
T-H to On 

00 On O 



O cor^ 

CN (N CN 



CO 00 00 

t^ T^ 00 

to O CO 



00 00 CO 
CN CO -^ 



CN O O 

CO C O 
T* lO to 



T-H to to 

NO rg CN 

t^ NO NO 



lO NO t^ 



to to UD 

CN CN CN 

NO NO NO 



to On f^ 

NO CN 00 
'^ On to 



CN T-H to 

■* On lO 
■^ CO CO 



NO to to 

O to CN 

CO CO CO 



Tf ■'-' T-H 
CO O t— 
CO T-H NO 



TJH NO l>. 



NO C~^1 CO 
CN NO NO 
Tf NO t^ 



00 Tt o 
to !>. On 



O CO ^ 

NO NO CO 

r^ i>- -^ 



CN O 00 

t^ On O 



NO T-H CN 
On CO t^ 

O NO r- 



t^ O CO 
CN CO CO 



00 CN -^ 
CO !>• T-H 
CN t^ On 



O CO NO 
CO CO CO 



00 to to 

CN CO J:^ 
r-~ t^ C 



00 T* O 

T^ to NO 



o o o 
o o o 
to to to 



to o o 

CN to to 

NO t^ t^ 



00 On O 



to O O 
CN to to 

NO t^ t^ 



ON O 



00 lO to to 

CN 00 CO ■^ 
CO O On 00 



r-H T-H C 



lO CO CN T* 
CN 0> f^ to 
CO CN CN CN 



On CN •<* 00 
On f^ to CO 
CN CN CN CN 



CN NO t— t^ 

■^ O t^ Tfi 

CN CN t^ CO 



O^ T-H fS T^l 
T-H CN CN CN 



■^ CN 00 »0 
CO CO CO T-H 
rfH t^ On t^ 



OC' CN CO NO 
O CO to t^ 



NO 00 to C^l 

t^ CO T-H NO 

NO On 1>- O 



t^ CO NO T-H 

CN to t^ C 

T-H T-H T-H CN 



"tJ^ T-H CN •<* 

T-H rh 00 CN 

ON 00 On T-H 



NO O CO i^ 

CO Tt^ Ttl Tti 



to CN -^ to 

to 00 CN NO 
O On T-H CN 



O CO t^ O 
^ '^ tJi to 



to ^H T-H •^H 

T-H On CO t^ 



lO CN t^ CN 

NO t^ r^ 00 



OO 00 OO 00 



O O O O 

o o o c 
lO to to to 



o c o o 
to o o o 
t^ o o o 



T-H CO T* to 



o c c o 
to o o o 
r- O O O 



CN rfi to NO 



c 



T3 c 



lO c 

be c 

"Z ^ 
2 c 

^ (D 

t. •— 



a: "^ 

Q..2 

c 



On O T-H CN CO •^^ to 



256 



PIPING 



a 



> 
u 

X 






Si 
O 

Q 
o 



(S 



c 

at 
O. 

a 

o 
U 

V 

H 

"3 

c 
o 



2 •- 



3 

a> 
H 



(d 









l^"^3CC^OCN r—C^X^ -TTw-C^ O'TNC^ 

O O ^ lt~* c^ O Lc uc -^, i/^ O O I'T ^- t-». 

. — r^c^jtx^irj'.— — oc •— *^, — Of^oc 

t^^OOC'^^'— Xt-T X-^*— t--iOcc 

X c^ it; ;n »— I 



3o I -c-r 



LCOr^ Oi^^ LCOO •— -Ott XLcio 
LCXO'^'^CN ^: — 1— C: 









x— 1-~ 2; ] :i; ■^ 23 

LC o C> "^ o o 



'T X O T+" lO o 
; O — t^ -^ X lO 

: Lc t^ o ^ X o 



__ ^ ^ — 



X — — - x-^-O oor^i 



OC NO •^ I— c> 

CN O CS lO O 

O -^ 1~- ; >— LT, 



r-^ i/~. rj- 
•^ iC 3 

O <-C ^ 



rf »OvO OC Cs '-1 



lO X '-I 



; i/~, TT X *^ Lc t~~ 

;o ■^ CN , O C" r^ 



3"0 



CLC o to 
-^lO X <^ 



■^«o o 

O <D «*5 
— X ^ 



-— X ,X 



LC C^ r>j 
-^ C: rq 



CN> TT »o t^ o r^ 



X r^t:^ 
'— CN CO 



CM ••-H O hr Lc o 

O «N O O *^- o 
^^t- O »0 I C" O "^ 



^a Ti- o 
ir^ O r^ 

•~ o ■^ 



^ T— ' y-^ y-^ CS 



"^ U-; X 
'^ -^ JTJ 






_.I^ re X iX '^ 



C'— •^r-jr'^'rr lOt^OC C^ — r^i 



'-rr- X 

X LT, C^ 
"^ T lO 

lO X »-| 
>— ^- rsj 



wCN'— CNC^TT OOLT- — x^-r- 



o 



*e I-O o 

>— LC C 



r^fCrj- iou-;t^ C^Oc^J •rri-cr^ ^^ 



J= X = I 



■^" O CN ; c^ X '-C -r- *e ir; 



— — rN :^i -^ -^ 



O fC t^ 
r^ !>i r^i 



C: C> '^ 
O r-» r^ 



^ CC CN 

U-: O t^ 



73 a 



^J; ^^\^- m, 
— — ^-,— OOOOOC XXX 



■^3 s 



cCNOio 



r<i O O 
X w fO 
f5 ■^ "^ 



r^ O O 
lO o <r) 
lO o \0 



t>- ^-1 lO 



■^ lO »o 

00 CX) QC 



r^iTt O 


o 


^ 


^ 


^_ 


^ 


X 


^] 


— 


^ 


r^ 


LC 


LC 


• torrj Cn 


c^ 


o 


3 


r^ 


3 


-si 


tc 


X 


O 


^ 


r^ 


J-^ 


^<Mrfir5 


X 


■" — 


1^, 


t-^ 


"^ 


r^ 


■■" 


u~- 


^^ 


X 


X 


X 



O O L/~. ^ C; f-f~, i-/~, O ^ ^ O "^ to LO it; 



n i? 



3 § 

a c 

s 

if c 



> -^ 



^ X o -e 



'-''-'CNr^rrs-^KJ'tou-j'or^x 



■--^ ! ■^^ ^— I rN 



-\ -\i -.\ j 



PIPING 



257 



Table 22. 


ApF 


>roximate Weight Per Foot of Lar 


ge( 


D. D. 


Pipe. 














THICKNESS, INCHES 












Outside 




























Diameter 








1 




1 












1 




of Pipe 


H 




Vl6 


1 




"/'l6 

1 


M 


I 16 




H 




i 




Inches 


Pounds 


Pounds 


Pounds 


Pounds 


Pounds 


Pounds 


Pounds 


Pounds 


14 


36 


71 


45 


68 


54 


56 


63.37 


72.09 


80 


72 


89 


27 


106 


00 


15 


39 


38 


49 


02 


58 


57 


68.04 


77.43 


86 


73 


95 


95 


114 


00 


16 


42 


05 


52 


35 


62 


57 


72.71 


82.77 


92 


74 


102 


62 


122 


00 


17 


44 


72 


55 


69 


66 


58 


77.38 


88.11 


98 


74 


109 


30 


130 


00 


18 


47 


39 


59 


03 


70 


58 


82.06 


93.45 


104 


75 


115 


97 


138 


00 


20 


57 


00 


65 


70 


78 


59 


91.40 


104.13 


116 


77 


129 


33 


154 


00 


21 


59 


20 


69 


04 


82 


60 


96.07 


109.47 


122 


78 


136 


00 


162 


00 


22 


62 


60 


72 


38 


86 


60 


100.75 


114.81 


128 


78 


142 


68 


170 


00 


24 


68 


00 


85 


00 


94 


61 


110.09 


125.49 


140 


80 


156 


03 


186 


00 


26 


74 


00 


93 


00 


102 


62 


119.44 


136.17 


152 


81 


169 


38 


202 


00 


28 


80 


00 


100 


00 


120 


00 


128.78 


146.85 


164 


83 


182 


73 


218 


00 


30 


85 


00 


107 


00 


128 


00 


138.13 


157.53 


176 


84 


196 


07 


234 


00 



Large O.D. pipe is generally made in outside diameters of from 14 to 30 
in., and in thicknesses ranging from ^ to ^ inches. Table 22 gives the 
weight of large O.D. pipe of standard thicknesses. 

Cold drawn steel tubing can be obtained in regular pipe sizes from 
5^ to 4 in. ; and in the standard, extra heavy and double extra heavy weights, 
as well as in special tubing dimensions and weights. 

The pipe weight should be selected to give durability and to maintain 
safety, rather than for initial safety. The standard hydrostatic test pres- 
sures, to which pipes are subjected at the mills, exceed even modern power 
plant pressures ; the initial ultimate strength of pipe is greater than any 
pressure stress likely to occur in ordinary practice. 

The following formula gives the approximate pressure at which pipe 
will burst : 

2 T S 
P=^ (17) 

P = Bursting pressure, lb. per sq. in. 

T := Thickness of pipe wall, inches 

D =: Outside diameter of pipe, inches 

S = Tensile strength of material, lb. per sq. in. 

Machinery's Handbook gives the value of S, determined by actual bursting 
tests, as 40,000 for butt-welded steel pipe and 50,000 for lap-welded steel 
pipe. Table 23 of bursting pressures, is based on the above formula. 

Butt-welded pipe in sizes 3 in. and smaller and lap-welded pipes in sizes 
3y2 in. and larger, are used in calculating the table. It is stated that the 
accuracy of the figures has been checked by exhaustive tests conducted by 
the National Tube Company. 

The pressures given in Table 23 are the approximate pressures at 
which new pipe will burst. In designing or selecting piping, a factor of 
safety is used ranging from six to fifteen, depending upon the severity of 
the service, the degree of exposure or corrosive action encountered, the dura- 
bility desired, and the probability of future operation at increased pressure. 

The second edition of the specifications issued by the Power Plant Piping 
Society recommends that all pipe (except boiler feed lines) be wrought steel 
with welded seams, butt-welded for the 2-in. and smaller sizes and lap- 
welded for the 2j^-in. and larger sizes. (General commercial steel pipe is 
butt-welded in the 3-in. and smaller sizes.) 





?»-!--,-,_ ■Ill 

iiiiiiiiiiiijj 
II II II II 11 II 11 

II nil II II II 11 

11 II II 11 11 II II 
5|IIIII!"ILW 

si II ffT^ 



^4V \^_ 



Old National Bank Building, Spokane, Wash., equipped with 
Heine Standard Boilers, 



P I P I N Tx 



259 



Table 23. Approximate Bursting Pressures for Steel Pipe. 



Size of Pipe, 
Inches 



BURSTING PRESSURE, POUNDS PER SQUARE INCH 



Standard 



Extra Heavy 



Double Extra Heavy 







13,032 
10,784 
10,384 


17,624 
14,928 
14,000 


28,000 






1 
i>i 


8,608 
8,088 
6,744 


11,728 

10,888 

9,200 


23,464 
21,776 
18,408 






2 
2K 


6,104 
5,184 
5,648 


8,416 
7,336 
7,680 


16,840 
15,360 
14,680 






13,714 
15,900 
14,970 



14,200 
13,480 
13,040 



11,470 
10,140 



Size of Pipe, Inches 



BURSTING PRESSURE, POUNDS PER SQUARE INCH 



Large O. D., 3^-in. Thick 



Large O. D., J^-in. Thick 



14 
15 
16 


2,680 
2,500 
2,340 


3,570 
3,333 
3,120 


18 
20 
22 

24 


2,080 
1,870 
1,700 
1,560 


2,770 
2,500 
2,270 
2,080 



For pipe sizes up to and including 7 in., standard wrought steel pipe 
should be used for saturated or superheated steam lines with a working pres- 
sure not exceeding 250 lb. per sq. in. and a total temperature not exceeding 
700 degrees. 

For saturated steam lines with a working pressure of not over 150 lb. 
per sq. in. the weight of pipe in pounds per foot should be 

24.69 for 8 in., 

34.24 for 10 in., 

43.77 for 12 in., 
and O.D. sizes should be from Vio to Vio in. thick. For saturated or super- 
heated steam lines with a working pressure from 150 to 250 lb. per sq. 
in. and a total temperature of not over 700 deg. the weight of pipe in pounds 
per foot should be, 

28.55 for 8 in., 
40.48 for 10 in., 

49.56 for 12 in., 
and O.D. sizes should be from ^U to '/lo in. thick. 



260 



PIPING 



For saturated or superheated steam lines with a working pressure of 
not over 350 lb. per sq. in. and a total temperature of not over 700 deg.. all 
pipe, up to and including 12 in., should be extra heavy, and O.D. sizes should 
be 5^-in. thick. For boiler feed lines with a working pressure of from 
200 to 400 lb. per sq. in., extra heavy wrought steel pipe should be used up 
10 and including 12 in., and O.D. sizes should be 3^ in. thick. If the water 
is extremely bad, the use of extra hea^y drawn brass pipe or extra heavy 
galvanized wrought steel pipe is recommended. 

For boiler feed lines with a working pressure of not over 200 lb. per 
sq. in. and with favorable water conditions, standard wrought steel pipe 
should be used for sizes to and including 7 in.; the weight of pipe in pounds 
per toot should be 

28.55 for 8 in., 
40.48 for 10 in., 

49.56 for 12 in. 

Extra heav3' wrought steel pipe, standard weight galvanized wrought 
steel pipe or brass pipe should be used when there is considerable corrosion. 



Table 24. Standard Iron Pipe Sizes. 



Iron Pipe Size, 
Inches 



ACTUAL DIAMETERS, INCHES 



Outside 



Inside 



APPROXIMATE WEIGHT, 
POUNDS PER FOOT 



Brass 



Copper 









1 



134 
2 



0.405 
0.540 
0.675 



0.840 




1.050 




1.315 


i 


1.660 




1.900 




2.375 


1 



0.281 
0.375 
0.484 



0.625 


0.822 


1.062 



1.368 
1.600 
2.062 



0.25 
0.43 
0.62 



0.90 
1.25 
1.70 

2.50 
3.00 
4.00 




8.30 
10. PO 



0.26 

0.45 
0.65 






95 


1 


31 


1 


79 



2.63 
3.15 
4.20 



6. 04 

8.72 

11.45 





4 


4.500 


4.000 


12.70 


13.33 




4H 


5.000 


4.500 


13.90 


14.60 




5 


5 . 563 


5.062 


15.75 


16.54 




6 


6.625 


6.125 


18.31 


19.23 



For blow-off lines for boilers operating with either superheated or sat- 
urated steam, extra heavy wrought steel pipe should be used. (Galvanized 
extra heavy steel pipe is preferable to black for this service.) 

For low pressure water lines, with a working pressure of not over 50 
lb. per sq. in., and with favorable water conditions, standard wrought steel 
pipe should be used for sizes to and including 7 in.; the weight of pipe 
in pounds per foot should be 

28.55 for 8 in., 
40.48 for 10 in., 

49.56 for 12 in., 

and O. D. sizes should be from Vs to Vic in. thick. When the corrosion due 



PIPING 



261 



to the water is extremely bad, or the pipe is laid in the ground, cast iron 
flanged pipe, built to American Water Works Standards, should be used 
exclusively. 

Seamless drawn brass and copper pipe can likewise be obtained in pipe 
sizes from ^ to 6 in., and in the standard and extra heavy weights. The 
actual inside diameter and the weights per foot of brass and copper pipe, 
Tables 24 and 25, differ from those of wrought iron. 



Table 25. Extra Heavy Iron Pipe Sizes. 



Iron Pipe Size, 
Inches 



ACTUAL DIAMETER, INCHES 



Outside 



Inside 



APPROXIMATE WEIGHT 
POUNDS PER FOOT 



Brass 



Copper 



H 
^ 



0.405 
0.540 
0.675 



0.205 
0.294 
0.421 



0.370 
0.625 
0.830 



0.389 
0.651 
0.872 



^ 


0.840 


0.542 


1.200 


1.260 


^ 


1.050 


0.736 


1.660 


1.743 


1 


1.315 


0.951 


2.360 


2.478 


IH 


1.660 


1.272 


3.300 


3.465 


m 


1.900 


1.494 


4.250 


4.462 


2 


2.375 


1.933 


5.460 


5.733 


2y2 


2.875 


2.315 


8.300 


8.715 


3 


3.500 


2.892 


11.200 


11.760 


3K 


4.000 


3.358 


13 . 700 


14.385 


4 


4.500 


3.818 


16.500 


17.325 


43^ 


5.000 


4.250 


19.470 


20.440 


5 


5.563 


4.813 


22.800 


23 . 940 


6 


6.625 


5.750 


32.000 


33.600 



Pipe Fittings 

T) IPE fittings are made of cast iron, malleable iron, cast steel, brass, or 
^ other alloys. 

Cast iron fittings are the most common, as they fulfill the usual service 
requirements. They are made in standard weight, for 125 lb. working steam 
pressure, and in extra heavy weight, for 250 lb. working steam pressure. 

. Malleable iron fittings are generally restricted to 2-in. or smaller sizes. 
In these they are used extensively on saturated steam lines and on boiler 
feed lines with working pressures of not over 250 lb. per sq. in. Malleable 
fittings are made in standard weight, for 125 lb. working steam pressure, 
and in extra heavy weight for 250 lb. working steam pressure. 

Cast steel fittings are now generally used on superheated steam lines, 
especially when the working pressure is over 200 lb. and the total tempera- 
ture is more than 500 degrees. They are made for superheated steam pres- 
sures as high as 350 lb. per sq. in. and for a total temperature of 800 degrees. 

Iron pipe-size brass fittings are made in two weights, — a standard weight 
for working steam pressures up to 125 lb. per sq. in. and an extra heavy 
weight for working steam pressures up to 250 lb. per sq. in. They are used 
onlv when brass piping is installed, which is rarely. 




o 



CS 

ID 

C 

CO 

w 

G 

"5 



Pu o 

O u 
O V< 

ffl CO 
0.C0 

s ^ 

o o 

^ > 
.2 ° 



C 3 

• '• GO 

D. u 
00 « 

c o 

spa 



Si 



PIPING 263 



Pipe fittings are divided into two classes, screwed and flanged. Screwed 
fittings are used generally in the smaller sizes. The making, and more par- 
ticularly the breaking, of joints is much easier with flanged than with 
screwed fittings. No hard and fast rule governs the limits within which 
each type of fitting should be used. Some authorities specify flanged fittings 
on all lines 2^ in. or larger, while others state that all fittings 4 in. or 
larger should be flanged. The present tendency seems to be to use flanged 
fittings on all lines larger than 3 inches. 

Standard weight and extra heavy cast iron flanged fittings are listed in 
sizes from ^ to 24 inches. Screwed fittings in the same material are listed 
in sizes from yi to 12 in., in standard weight ; and from ^^ to 12 in., in the 
extra heavy. 

Extra heavy cast steel flanged fittings, for 350 lb. pressure, and 800 deg. 
total temperature, are listed in sizes from 1^4 to 24 inches. Similar screwed 
fittings are listed in a more limited range, from about 3 to 6 inches. 

Iron pipe-size brass flanged fittings are made in a limited range in 
standard weight (from about 2 to 6 in.), but extra heavy brass flanged fit- 
tings can be obtained in any of the extra heavy cast iron patterns. Iron 
pipe-size brass screwed fittings are listed for 125 lb. pressure in sizes varying 
from about % to 4 in., and in cast iron patterns, for steam pressures up to 
250 lbs., in sizes varying from ^ to 6 inches. 

Malleable iron screwed fittings for 125 lb. pressure are listed in sizes 
from Ys to about 7 inches. Extra heavy malleable screwed fittings, for 250 
lb. pressure, are listed in sizes from ^ to about 6 inches. 

Only the thread dimensions of screwed fittings are standardized. Un- 
fortunately the other principal dimensions have not been standardized, as 
have those for flanges and flanged fittings. Consequently the dimensions of 
screwed fittings vary widely with the different manufacturers. 

The American Standard dimensions of flanges and flanged fittings are 
accepted and used by nearly all manufacturers. The complete standard in- 
cludes sizes up to 100 in. diameter. The standards most used, from 1 to 48 
in., are given in Tables 26 to 29, the first two being for 125 lb. and the other 
two for 250 lb. working pressure. The letters in the tables of fittings refer 
to the lettered dimensions in Fig. 143. 

The following explanatory notes apply to the tables of flanges and flange 
fittings : 

a — Standard and extra heavy reducing elbows carry same dimen- 
sions center to face as regular elbows of largest straight 
size. 

b — Standard and extra heavy tees, crosses and laterals, reducing 
on run only, carry same dimensions face to face as largest 
straight size. 

c — All extra heavy fittings and flanges to have a raised surface 
Vie in. high inside of bolt holes for gaskets. 

d — Standard weight fittings and flanges to be plain faced. 

e — Bolt holes to be % in. larger in diameter than bolts. 

f — Bolt holes to straddle center line. 

g — Face to face dimension of reducers, either straight or eccen- 
tric, for all pressures, shall be the same face to face as given 
in table of dimensions. 

h — Square head bolts with hexagonal nuts are recommended. 

i — For bolts, l->^-in. diameter and larger, studs with a nut on 
each end are satisfactory. 

j — Specifications of long radius fittings refer only to elbows 
made in two center to face dimensions. These are to be known 
as elbows and long radius elbows, the latter being used only 
when so specified. 



264 



PIPING 



The general methods of cofinccting pipe are by coupHngs, nut unions, 
or flange unions. The first two are screwed connections, and the last can 
be made with a gasket or with metal-to-metal seats. 

Couplings are made of cast iron, standard or extra heavy, from about 
^2 to 3 in. ; of malleable iron, in standard weight from ^ to 6 in. ; of brass, 
in standard weight, from y% to 4 in. ; and in extra heavy weight, from ^ to 6 
inches. They can be obtained in all three materials ; threaded right-hand, 
or right and left. Couplings should be used only for the smaller sizes of 
pipe. 



hAH 




w 



J 



90* Ell 




Double BranchEH 




SidcOutleVEM 




LongRodiusEU 




4-5-EII 



•-A-4-i-A-» 



"XlF] 



T<t«. 



i»rA-|-A-» 






-A-i-A 



t^_ 



DooUe SvyccpTee 




Side Out lot Te^ 



■ A^A- 



Cross 



■^iiiiJ 




LQ+ero^ 



K-G-^ 





Reducer 



Eccentric Reducer 



Fig. 143. Standard Types of Flanged Fittings. 

Tables 26 and 28. 



Dimensions in 



PIPING 



265 



Table 26. American Standard Dimensions for Flanged Fittings for 
125 Pounds Working Pressure. (See Fig. 143.) 



SIZE 


'i 


0) 

« 
A-A 


O 
u 

a 

0) 

O 
A 


u 

B 


« 

•girt 
c 


« 
_=« to 

^^ 

D 


« 
P^ 

^ 2 

-, 0) 



E 


a; 
F 


0; 
3 

G 


C 

"0 
>^ 

0) 
-P 

s 




fin 

& 

C 

IS 




1 
1 

6 


% 
1 

s 




1 

1^ 


7 1/2 

8 


33^ 
3^ 
4 


5 

53/2 

6 


IM 

2 

23^ 


73/^ 

8 

9 


5M 
63^ 

7 


IM 
IM 
2 




4 

43/2 
5 


7 
16 

Yi 
9 

16 


3 

3^8 

3^ 


4 
4 
4 


7 
16 

7 
16 

¥1 


7 

T6 

1% 

_7_ 
16 


2 
3 


9 

10 
11 


43^ 

5 

53^ 


63^ 

7 

7M 


23/^ 

3 
3 


103/2 

12 

13 


8 

93^ 
10 


23^ 
23^ 

3 


(> 


6 
7 
73^ 


11 
16 


4M 
53^ 
6 


4 
4 

4 




7 
16 

7 
16 

7 
16 


33^ 

4 

4K 


12 
13 
14 


6 

63^ 

7 


83^ 

9 

93^ 


33^ 

4 

4 


143^ 
15 

153^ 


113^ 

12 

123^ 


3 
3 
3 


63/2 

7 
73/2 


83^ 

9 

93^ 


13 
16 
15 
16 
15 
16 


7 

73^ 

7M 


4 
8 

8 


'A 

% 


7 
16 

3^ 
3/2 


5 

6 

7 


15 
16 
17 


73^ 

8 

83^ 


103^ 
113^ 

12M 


43^ 

5 

53^ 


17 
18 
203^ 


133^ 
143^ 
163^ 


'SV2 
33^ 
4 


8 

9 

10 


10 
11 

123^2 


15 
T6 

1 
ll^ 


83^ 

93^ 

lOM 


8 
8 
8 


% 
% 
% 


3^2 

9 

16 

^8 


8 

9 

10 


18 
20 

22 


9 
10 
11 


14 

153i 

16M 


53^ 
6 

63^ 


22 
24 
253^ 


17H 
193^ 
203^ 


43/^ 

43^ 
5 


11 

113^ 
12 


13 >2 

15 

16 


13^ 
13/8 
ll^ 


11% 

133^ 

143^ 


8 
12 
12 


% 
% 


y% 
11 

16 

% 


12 
14 

15 


24 
28 
29 


12 
14 
14M 


19 
213/^ 

22M 


73^ 
8 


30 
33 
343^ 


243^ 

27 

283^ 


6 
6 


14 
16 
17 


19 
21 

223<C 


I3i 
1^ 


17 

18M 
20 


12 
12 
16 


1 
1 


13 
16 

y% 


16 
18 
20 


30 
33 
36 


15 

163^ 

18 


24 

263^ 

29 


8 

83^ 

93^ 


363^ 

39 

43 


30 
32 
35 


63^ 

7 
8 


18 
19 
20 


233^ 
25 

273^ 


ii^ 

1 JJ^ 

J^ 16 


21 3i 
22M 
25 


16 
16 
20 


1 
13^ 

13^8 


1 

ii^ 

\y 


22 
24 
26 


40 

44 
46 


20 

22 
23 


313^ 

34 

363^ 


10 
11 
13 


46 

493^ 

53 


37 3i 
40>^ 
44 


83/2 

9 

9 


22 
24 
26 


293^ 

32 

343i 


IH 

1>^ 

2 


273^ 
293^ 
31% 


20 
20 

24 


1% 
l3i 


ii% 
13^ 

lA 


28 
30 
32 


48 
50 
52 


24 
25 
26 


39 

413^ 

44 


14 
15 
16 


56 
59 


463^ 
49 


93^ 
10 


28 
30 
32 


363^ 
38^ 
41^ 


9 J- 

■^16 

2>^ 
2W 


34 
36 

38 U 


28 
28 
28 


13^ 
IH 
IM 


1^8 
ii^ 

134 












34 


54 
56 
58 


27 
28 
29 


463/^ 

49 

513^ 


17 
18 
19 








34 
36 
38 


43 M 
46 

48 M 


2l'6 

23/8 

2^/^ 


403^ 
42% 
453^ 


32 
32 
32 


13^ 
13^ 


1 -^ 


36 








1^ 


38 








1 y 








40 


60 
62 
64 


30 
31 
32 


54 

563^ 

59 


20 
21 
22 








40 

42 
44 


50M 

53 

553^ 


23^ 
2^ 
25/^ 


4734 
493^ 
51% 


36 
36 
40 


1^ 
1^ 
1^ 


1% 
1 11 


42 








44 








v^% 








46 


66 

68 


33 

34 


613^ 
64 


23 

24 








46 
48 


573^ 
593^ 


oil 

•^16 

2M 


53% 
56 


40 
44 


1^ 

1^ 


1 J-5 


48 






















A'^Mf unions are made with malleable iron, steel or brass bodies, with 
gaskets or with brass or bronze seats. The commercial size range is from 
]4, to 4 in., but they are not used in sizes larger than 2 inches. Nut unions 
are not intended primarily for high pressure work ; for low or medium pres- 
sures however the connection is satisfactory and easily broken. Their use 
permits desirable piping layouts and connections that would otherwise be im- 
practicable. Unions with brass or bronze seats are usually preferable to the 
all-iron gasket type. 



PIPING 



267 



Table 27. American Standard Dimensions for Pipe Flanges for 
125 Pounds Working Pressure 



Diameter 
of Pipe, 
Inches 


Diameter 

of Flange, 

Inches 


Thickness 

of Flange, 

Inches 


Width of 
Flange 
Face, 
Inches 


Diameter 
of Bolt 
Circle, 
Inches 


No. of 
Bolts 


Diameter 

of Bolts, 

Inches 


Diameter 
of Bolt 
Holes, 
Inches 


1 

IM 


4 

43^ 

5 


1^ 

16 


1^ 
1% 


3 

3^ 
3K 


4 h 
4 1^ 

4 3^ 


1^ 
9 

16 


2 

2^ 

3 


6 

7 
73^ 


n 

16 
% 


2 

2K 
2% 


4% 4 
5H 4 
6 4 




% 
% 
% 


3M 
4 

43^ 


83^ 

9 

9M 


13 
16 

15 
16 


23^ 
23^ 

2% 


7 

73^ 

7% 


4 

8 
8 


% % 
% % 
% % 


5 
6 

7 


10 
11 
123^ 


15 
16 

1 
1^ 


23^ 

2% 


83^ 8 

93^ 8 

10% 8 


% 
% 
% 




8 

9 

10 


133^ 

15 

16 


13^ 


2% 

8 

3 


11% 8 
13% 12 
14% 12 


% 
% 


Vs 
Vs 
1 


12 19 

14 21 

15 221^ 


1% 
1% 


33^ 
33^ 


17 i 12 K 1 
18% 12 1 IH 
20 16 1 13^ 


16 
18 
20 


231^ ! l^ 
25 1 1^ 
27K 1 IH 


33^ 
3% 


21% 
22% 
25 


16 
16 
20 


1 

1^ 

13^ 


13^ 
1% 


22 
24 

26 


293^ IH 
32 IJ^ 
341^ 2 


3% 
4 

43^ 


27% 
293^ 
31% 


20 
20 

24 


1% 
1% 
1% 


1% 


28 
30 
32 


36M 
38% 
41% 


2^ 

23^ 
2% 


4% 
4% 
4J^ 


34 1 28 
36 28 
383^ 28 


1% 
1% 
13^ 


1^^ 
1^ 


34 43M 2^ 4K 403^ 
36 46 23^ 5 42% 

38 48% 1 2% 53^ 45K 


32 
32 
32 


IK 
13/2 
1^ 


1^/^ 
1^ 
1% 


40 
42 
44 


50% 
53 

55K 


23^ 
2^ 
2^ 


5% 
5^ 
5^ 


47% 
493^ 
51% 


36 
36 
40 




1% 
1% 
1% 


46 
48 


5734 
593^ 


9 li 

^16 

2% 


5^ 
5% 


53% 
56 


40 
44 


1% 


1% 
1% 



Flange unions are of two general types, those with cast or malleable 
bodies and brass-to-brass or brass-to-iron seats, similar to those of nut 
unions ; and those in which a gasket is used. 

The first type is expensive and, although made in sizes from I/2 to 12 in., 
its use in practice is limited to the smaller sizes. It has an advantage for 
connections that must be often broken and remade. 

The second and more common type of flange union is that in which the 
pipe ends to be connected are secured in or by two metal flanges ; a gasket 
is inserted between the flanges and the flanges are drawn together by bolts. 
The most satisfactory forms of this type of union are the screwed joint, 
the peened joint, the lapped or Van Stone joint, and the welded joint. Fig. 
144 gives examples of these four joints. 



268 



P I P I X G 



Table 28. American Standard Dimensions for Flanged Fittings for 
250 Pounds Working Pressure. (See Fig. 143.) 



SIZE 







<— X 


























OS 


o 










M 


t£ 










e> 










a 








;:^ 




^ 




S 


r=* = 


,S X 


.^ 


u 


u 


. 


^ 








^** 


9 


eS 


r^ '"^ 




o 


ct 


:« 


3 












d 


^ 


- S 




S3 m 


'^m 


fe„ 


C3 b 


o 


o 


O 


■fca 


o 


P=4 

o 
o 


o 

Li 




O S3 


51 


51 

3^ 


O 3 


1 


c 


Ci 


O 




^ 


9 




^^ 


n^ 


C_3 


§-1 


^- 


.2 


.2^ 


6 


ea 


rC4 


— ' 


^ 


^ 


&4 








a 




~ 


z: 


^ • 


A-A 


A 


B 


C 


D 


E 


F 


G 













1 

11.^ 



9 



4 

4M 
4K 



0>9 

6 



23^ 
2^ 



8H 
11 



6>2 

8M 



2K 
23^ 



4M 
5 
6 I 



16 

13 
16 



3^ 
3^ 

4H 



^2 



E a 



1^ 

1 ^ 



2 
3 



10 
11 
12 



53- 
6 



7H 



3 113^2 

3 3^1 13 
3K!l4 



9 

103^ 
11 



2H 
2M 
3 



6 



63^ 

814 



3^ 
1 



o 

6^ 



^1 



4 



33^ 

4 
41.^ 



13 
14 
15 



6>2 

7 

71^ 



9 

91^ 



4 

43^ 

414 



16 
17 
18 



83^11^ 
9 il2M 



53^ 
6 



iD}4\i2y2 
iQYoii^yo 

18 1 143^ 
18^ 
213^1 
231^ 



3 I 7 
3;^' 71-^ 



9 
10 

1034 






734 

7J^ 
8H 



741 



15 I 339 . .. 
17Ki 4 I 9 
19 43^ 10 



11 

12J^ 

14 



1^8 

llv 



9^ 
10^8 



IJillJi 



8 


'-^i 


12 


''A 


12 


's' 



12 126 1 13 

14 |30 15 

15 31 1 151^ 



19 
21^ 

22M 



8 133391273^9 6 14 203^ 
83^^1373^^131 i 63^116 |23 

9 1393^133 I 63^^(17 \2A.Vo 



2% 
2^ 



173^116 
20Mi20 
213^^120 



Us 



16 

18 
20 



133 
i36 
139 



163^ 
18 



24 

263^ 



191^29 



93^^ 
10 



42 
451/^ 



10i^'49 



3434 
373^ 
403^ 



73^il8 
8 19 
83^!20 



253/9 
28 

303^ 



2^122^ 

2^824M 
23^'27 



20 
24 

24 



13^ 



16 

H 



16 

% 
13 
16 



s 


20 


10 


14 1 


6 


25^^!20i9, 


5 ill 


15 


1% 


13 12 


s 


16 


y 


21 


103^ 


15K! 


61^ 


273^^1223^9: 


5 


113^ 


IBK 


Wa. 


14 


12 


1 1 \ 


% 


10 


2:3 


iiVo 163^1 


7 1293 9i24 ! 


51/i 


12 


171^ 


VA 


15M' 16 


! 1 ! 


15 
16 



1 ^- 

^ 16 



114 
1^-8 
Wo 



22 
24 
26 


41 
45 

48 


2Qy> 
22 >| 
■^,4 


313^ 

34 

363^ 


11 
12 
13 


53 
571^ 


43 >^ 
47^ 


93^ 
10 ■ 


22 

'24 
26 


33 
36 
38^ 


2% 

2H 

2M 


29M 

32 

341^ 


24 
24 

■^8 


132 


ll^ 

1 i^ 
















28 


52 
55 

58 


26 

271^ 

29 


39 

41K 

44 


14 


1 


■?8 


40M 
43 

45H 


2H 
3 

3H 


37 

39 H" 
413 9 


28 
28 
■■»8 


1?8 
1^4 
IJ'8 


1 '^ 


30 


15 

16 






30 

32 


2 


32 






■v; 












34 


61 
65 
68 


301 9 461 9 


17 






34 


47I/2 
50 

52 M 


3M 


43H 

46 

48 


28 
32 
32 


1^8 


?.H 


36 


323^ 
34 


49 
513^ 


18 
19 









36 
38 


23s 


38 








2i% 












40 


71 
74 
78 


35>9 

37 

39 


54 -^0 






40 


•5439 
57 
59 K 


^16 

3H 


bOH 
52M 

DO 


36 
36 
36 


VA 
2 


•>_2_ 


42 

44 


563^^ 
59 


21 
22 




•::J:::: 


42 
44 


Oil 

- 16 
13 

- 16 


46 
4S 


81 
84 


403^2|6U2i23 : 

42 |64 ,24 j.... ,....,.... 


46 
48 


6U2 
6b 


4 


37 }4 
603:r 


40 
40 


2 
2 


2,^ 
3 



In the screwed joint, the flange is screwed on the pipe until the pipe 
projects about Vie in. bej-ond the face of the flange. A facing cut is then 
taken across the face of the flange and the end of the pipe. The face of the 
flange should then be square with the axis of the pipe and the gasket should 
bear on the end of the pipe. This joint is accepted for all sizes of pipe in 
saturated steam lines with working pressures not greater than 125 lb., on 
boiler feed lines with working pressures up to 150 lb., for blow-off lines, 
and for low pressure water lines. It is also used on medium and high pres- 
sure saturated and superheated steam lines and boiler feed lines in sizes up 
to about 8 inches. 



rrfil Ihn 



H^l IP 




269 



:iD 



o^EZi 



^ 



Fig. 144. Typical Flange Joints. 



Table 29. American Standard Dimensions for Pipe Flanges for 
250 Pounds Working Pressure 



Diameter 
of Pipe, 
Inches 


Diameter 

of Flange, 

Inches 


Thickness 

of Flange, 

Inches 


Width of 
Flange 
Face, 
Inches 


Diameter 
of Bolt 
C ircle. 
Inches 


No. of 
Bolts 


Diameter 

of Bolts, 

Inches 


Diameter 
of Bolt 
Holes, 
Inches 


1 

1^ 

1^ 


5 
6 


H iM 

^ ! m 


3^ 
43^ 


4 K 1 H 

4 1 % 1 M 


2 

2M 
3 


6>^ 


!i : 2M 
1 21^ 
iH 2^ 


5 ! 4 

5% 4 
6^ 8 


% i % 

K I K 

K :^ 


3^ 

4 

4M 


9 
10 

103^ 


1^ 2M 7M 
IM 3 7K 
1^ 3 8>^ 


8 
8 
8 


K J^ 
K K 
K ; K 


5 
6 

7 


11 iH 

123^ li^ 
14 1^ 


3 1 9M 

3^ UK 


8 1^ Ji 
12 1 ^ >^ 
12 1 K 1 


8 

9 

10 


15 

16M 
173^ 


1^/^ 33^ 
IM 3^ 


13 
14 
15K 


12 
12 
16 


y% 1 1 
1 13^ 
1 iK 


12 20M 

14 23 

15 243^ 


2 4M 

23^8 43^ 
2^ 4M 


17^ 
20M 
21 H 


16 1 13^ 
20 1^ 
20 1 IK 


IK 
IK 
IK 


16 
18 
20 


25^ 1 2K 
28 1 2% 
303^ 1 23^ 


-t^ 1 223^ 

5 24M 
53^ 27 


20 IK 
24 , IK 

24 , 13^ 


IK 
IK 


22 
24 
26 


33 
36 

383^ 


2^ 5M 
2H 6K 


29M 24 IK 
32 24 1^ 
343^2 28 ]^ 


IK 
IK 
IK 


28 
30 
32 


40M 
43 

45 1< 


2M 
3 

33-^ 


63^ 

6^ 


37 28 
39 K 28 
413^ ! 28 


1^8 

IK 


IK 
IK 
2 


34 
36 
38 


47^ 
50 

52i<r 


3M 
3H 
3i^ 


7 
7H 


43 K 28 
46 32 
48 1 32 


1% 


2 
2 
2 


40 
42 

44 


543^ 

57 

5914 


3^ 7H 

3H T3^ 
3M TVs 


50 M 36 
52 M 36 
oh 36 


ivs 1 2 
i.K 2 

2 23^8 


46 
48 


613^ 
65 


4 


7% 
8^ 


57^ 
60^ 


40 
40 


2 
2 


2K 

2K 




OS 
O 



C3 



C i- 
l) V 

^ o 

V QQ 

o-c 

^° 

u O 

wg 

o „ 



PQ 



ffl 



u u 

^ a 
o 

- >> 

u to 

u a 

U 

•^ 00 

-oH 
c 
a . 

w£ 

C ffl* 

X3 
o 

o_a 
c^ 
.25: 

4-1 

CO 

.s 

o 

o 



,l^yl^^-^^^>\^#x 



PIPING 271 



The peened joint is formed by shrinking a flange onto the end of the 
pipe, which is peened or expanded into a recess in the face of the flange. 
A light facing cut is then taken across the face of the flange and the end 
of the pipe. This joint is better than the simple screwed flange, especially 
for sizes larger than 6 in., but cannot be made up well at the place of erection. 

The lapped or Van Stone joint, one of the most flexible in use, is made 
by upsetting and flattening the heated end of the pipe so as to form a flare 
oi lap. The flared end is faced to insure uniform thickness and a tight 
joint. The lapped portion of the pipe is also finished on the edge. The 
flanges are loose on the pipe, their hubs being bored slightly larger than the 
outside diameter of the pipe, and simply serve to draw the lapped ends of 
the pipe against a gasket. In some forms, the lapped part of the pipe is 
not of uniform thickness but tapers toward the edge; the face of the flange 
inside the bolt holes are then faced to the angle of inclination of the back 
side of the lapped part of the pipe. The lapped joint is recommended for 
practically all kinds of service. It is especially valuable on high pressure 
superheated steam lines and high pressure boiler-feed lines. 

The ivclded joint is made by welding a flange on the end of the pipe. 
Theoretically this is the nearest perfect of all joints, because a welded flange 
becomes a part of the pipe itself. Its success depends upon the care with 
which the weld is made. In practice the welded joint is reliable and satis- 
factory and is considered to be the best for high pressures and high de- 
grees of superheat. 

There is little choice between a well-made lapped joint and a well-made 
welded joint. Both are more expensive than the simpler types, but in high 
pressure work their cost is more than justified. 

Flange materials. Cast iron, malleable iron, cast steel, wrought steel and 
brass are used for flanges. Cast iron flanges are extensively used on sat- 
urated steam lines, boiler feed lines, and low pressure water lines. 

Malleable iron flanges are not as common as cast iron flanges, but are 
applicable to the same service. 

Cast steel and wrought steel flanges are recommended for high pres- 
sure saturated and superheated steam lines, high pressure boiler feed lines, 
and blow-ofif lines. 

Brass flanges are used only with brass pipe and almost exclusively in 
the screwed type of joint. 

The following figures, due to the Crane Company, show the ultimate 
strength of pipe flange metals : 

Ultimate strength. 
Material lb. per sq. in. 

Cast iron, ordinary grade 14,000 

Gray cast iron, high grade 22,500 

Malleable iron 37,000 

Forged steel 51,000 

Cast steel 67,000 

Valves 

VALVES control to a great extent the safety of a plant. Their location 
determines the flexibility of the piping system, either in normal opera- 
tion or in times of emergency. 

Safety valves for boilers generally must comply with the specifications 
of local or national codes. The A. S- M. E. Boiler Code requires that they 
shall be of the direct spring-loaded pop type, with seat and bearing surface 
of the disk either inclined at an angle of about 45 deg., or flat at an angle 
of about 90 de^. to the center of the spindle, 



272 



PIPING 



The safety valve charts. Figs. 145 and 146, may be used for determining 
the proper number and sizes of safety valves required. The charts are made 
up so that it is necessar\- to take only the rated horsepower of the boiler and 
run up the vertical line to the slanting line corresponding to the relieving 
pressure desired, and the proper size and number of safety valves are indi- 
cated at the left of the zone in which the vertical horsepower rating line 
crosses the relieving pressure line. If the intersection comes on a zone divi- 
sion line, the smaller valves are to be used. 

Exam pic. One 806 H.P. boiler to operate at 190 pounds gage pressure. 
The two-valve chart stops below 806 H.P. Therefore, wc must go to the 
three-valve chart. We hnd that the 806 H.P. vertical line does not inter- 
sect the 190 lb. pressure line. This indicates that more than three valves 
are necessary. We then take one-half the rated horsepower, and find that 
two 4 in. safety valves will relieve 403 H.P. The proper valve specifica- 
tion in this case is therefore four 4 in. safetv valves. 













\ 


1 






1 


1 




1 


; 


ill 


1 


1 






1 




— 














1 










1 


1 








1 1 1 


i 


t 
































1 


M'A/ 


y. 


^/ 


4A4^AZ^ 




^ 


'^ 
















Al 

















1 


W^/TV-^ 


w^ym^^. 


1 
















1 














' //y/v/y/yyA<^'<^^^ 
























. i 














/I/ ///l/^/X/XVV'.^// 


^ 




























Ui 4 

N J. 


















/A// 


Y//A^^. 


<<^ 


^y. 


^\ 
































-J 














/ 


T/T/^ 


-y^ 


w 


i 


1 


























0) 1 














t//y//y 


%^^$^^ 


y 


\ 


1 






























III ^ - 














>A////// 




1 


1 






























> 












u 


\LuML^/y/z//yyy 






! 
































H 




-i 










7/////////: 


/ZA^Za 










1 






































-j/=/'?U^/^AS^i4y0^M^^^ ' 




~ 


— 


— 












































//////// //y/Vy'Oy^ 


t 






1 


























1 


I ^ 








////////y/ 


<^^ 


1 


1 


1 


\ 


1 


1 


1 


























111 1 

li. 3' 
< 




-* 

1- 




_j 


//////v///y^ 








1 


1 


1 


1 


t 


RELIEVING 


CAPACITIES 


OF 








^^^^^P^^ 






1 


1 
1 






i 






1 


1 ,TWO 


_J_ 1 










cn ,, 


' ^ 


v/7/M^:^^^ 










1 






1 


1 1 










'^ 


zmnmiumir 


1 


























1 




5A 

si 


FETY VALVES j 










1 

2i' 


o 


iminiuif// 






























FL>T 


.ATS 1 , 1 1 INT. LIFt. 






mm m ' 




- 




- 




























A. S. M. E. STO'. 1 1 


I 






% 


m 


'Ml 


'Ml 


IL 




_ 




_ 




























1 1 1 1 i 1 1 1 


a/'/^o 1 



60 lao MO 180 22U 260 300 340 380 420 460 500 540 580 620 660 700 740 780 820 B. H.P. 

BOILER HORSE POWER. 
Fig. 145. Relieving Capacities of Two Ashton Safety Valves. 





















































































) 














































4}' 

1 


z 










/ 




/ 








> . 


y . 


^ y 


^^^ 


^1^ 


^^ 


^^ 




^ 








^ 


<-' 














K^ 


•~y 


X 


v^. 


[^.^ 


k3 


yp^ 


^•^ 


f\'=>$> 


[?^ 


r^ 


i^^ 


\^;y< 


i^ 


y 


^ 




















^i^ 


^k 


K 


y 


y. 


K'- 


^l^ 


'^^ 








X^ 


^ 
















• 1 










/ 


/. 


y.' 


^u 


^ 


y 


iK 


A 


^ 


ry 


y 


< 


'y 




y^^ 


^^ 


^ 




















0) 4 










/ ^ 


/\/ 


y 


n^ 


y 


y 


'y, 


y' 


\r 


-^A 


r^' 


^ 


y^ 


y^ 


>;> 


























N '. 








/ 


/ 


/[/ 


X 


^.^ 


X. 


X 


^ 


t^ 


-'P 


W. 


^ 


'^y 


' 


























m'l 


\ 




^.^ 


\/ 


A'' 


X 


X 


IK 


y. 


y 


^ 


-^< 


y^ 


■^y 


1 
























1 
1 1 Y 




f 


/J 


^y 


^^ 


X 


kM 


^^^^ 


K^ 


K> 


^^■i*^ 






1 




1 


\ 














^ T 


> 


\^ 


t/ 


y\/ 


//} 


V; 


yy 




^iS>" 










1 


1 






1 


















<3r 


X. 


yy^v^^A^/ 


y^^^.^^^i^i^j^ 


^ 


1 














1 


























/ 


^/K 


y" 


Wyy^^^.^^ 














































,, 


V, 


^/h 


^ 


y'yyzz^.^:::^ 


1 












































'c ■ 


>/P^;>;j^^>^;>::>:P::^;^^:;:> 


^ 


\ 


1 














































u 1 

iZ 3' 
< 


z 


<;<^^^;^^^^;^ 


y< 






\ 




















RE 


LIEV 


ING 


CAPACITIES 


OF 






j;^^^^ 


f$^^^^^ 


i 




\ 






















1 


T 




1-1 1— 


r- 














CO ■ 


'^ 


p^ 


'^1 








1 


























1 


HrM:. 

1 1 


^1 














> ■ 


-J 


f/ 


Y\ 




































1 


SAFETY VALVES 










»• 


u 


1 






\ 


































FLAT SEATS | | | | "NT 


L 


IFT. 






l| 










1 








































ASM 


e:. 9td'. 












i 


1 










1 






































i ! 


1 1 1 






Y*. 


ao 



7M3M 340 380 420 460 500 540 580 620 660 700 740 780 820 860 900 »40 980 1020 1060 

0OILER HORSE POWER. ' "' 

Fig. 146. Relieving Capacities of Three Ashton Safety Valves, 



PIPING 273 



Safety valves are also discussed in Chapter 16 on OPERATION. 

Globe valves, probably the most common type of stop valve, can be used 
simply as a stop valve, or also to partly throttle the flow of a fluid. These 
valves should be installed so as to close against the pressure, because if 
the pressure acts above the disk and the latter becomes detached from the 
stem, they cannot l)e opened. A further advantage in closing globe valves 
against the pressure is the ease of packing the spindle stuffing box when the 
valve is closed. These valves should not be placed in a horizontal return 
line, especially with the stem vertical, because the condensate must fill the 
pipe al)Out half full before it can flow through. The glol)e valve should 
be designed so that it can be packed under full line pressure and so that 
the disk or the scat can be quickly repaired. 

Valves with outside screws are preferable to those with inside screws, 
unless the screw must be protected because of the valve location. The out- 
side screw type indicates more quickly whether it is open or closed. This 
is especially true of the type having a rising stem or spindle and a stationary 
wheel. 

Globe valves are made in both screwed and flanged types, with brass, 
iron or steel bodies and with composition, babbitt, bronze, nickel and nickel 
alloy disks and seat rings. 

Standard pattern screwed brass globe valves, rated for about 150 lb. 
working steam pressure or 250 lb. working water pressure, are made in 
sizes from V^ to 3 inches. Extra heavy screwed brass valves, rated for about 
300 lb. working steam pressure, or about 500 lb. working water pressure, are 
made in sizes from % to 3 inches. Flanged standard brass valve sizes range 
from 34 to 3 inches. Extra heavy flanged brass valves are made in sizes from 
^4 to 3 inches. Brass globe valves are not commonly more than 2 in. 
diameter. Their use is limited to saturated steam lines, boiler feed lines 
and water lines of medium or low pressure. 

Standard pattern iron-body screwed globe valves, rated for about 150 lb. 
steam or 250 lb. water pressure, are made in sizes from 2 to 12 in., and the 
same type flange is made in sizes from 2 to 24 inches. Extra heavy iron-body 
globe valves, rated for about 250 lb. steam or 400 lb. water pressure, are 
made in either screwed or flanged types, and in sizes from 2 to 12 inches. 
Iron-body valves Avith disks, seat rings and spindles of other materials, are 
satisfactory for saturated steam lines, boiler feed lines and water lines with 
pressures up to their ratings, but are not so good as steel valves for pres- 
sures over 150 pounds. Valves 6 in. and larger should be equipped with 
by-passes, especially for the higher pressures. 

Steel valves should be used in superheated steam lines and high pres- 
sure feed lines. These are made in sizes from 2 to 12 in., in the extra 
heavy weight, and are rated for 350 lb. working steam pressure. 

Disks for globe valves are made of a wide variety of materials. Com- 
position disks are made in several grades ; soft for low pressure water, 
rubber for cold water up to 250 lb. pressure, semi-hard for hot water and 
boiler feed lines, hard for steam lines up to 150 lb. pressure. Babbitt metal 
disks are often used in low pressure hot water and steam lines. Brass or 
bronze disks are used in high pressure saturated steam lines and feed lines, 
the harder grades for the higher pressures. Nickel and alloys high in nickel 
are recommended for the highest pressures and for superheated steam. Valve 
seats, or at least seat rings, should be made of non-corrosive metal of 
characteristics similar to those required of metallic disks. 

Gate valves offer a minimum resistance to the flow of a fluid, but when 
throttled are hard to regulate and are likely to chatter. They are made of 
the same materials as globe valves and are applicable to the same types of 
service, except for throttling. For higli class installations, particularly in 
the larger sizes, gate valves represent the best standard practice. By-passes 
should be used with high pressure gate valves of 6-in. or larger diameter. 



274 PIPING 



A stop valve should not be placed in a vertical steam line, unless it is 
possible to drain the condensate that collects above the valve seat when the 
valve is closed. 

Automatic non-return valves should be installed on each boiler when the 
plant contains more than one. These valves automatically equalize the pres- 
sures of the different boilers, tliereby tending to equalize the loads. They 
can be used to cut in or cut out boilers automatically, will automatically cut 
a boiler off the line in case of an internal rupture, and will prevent steam 
being accidentally turned into a cold boiler. 

These automatic valves are made in man}- forms, all essentially check 
valves, although they may be stop valves as well. The control can be re- 
mote non-automatic, as well as hand and automatic, so that their automatic 
action can be tested at any time. 

The non-return valve should be carefully made and should be extremely 
rugged, because it is subjected to great stresses. It is usualh' attached di- 
rectl}' to the boiler nozzle, so that the boiler must be shut down if the valve 
has to be repaired. Besides the non-return valve, a gate valve should be 
placed between each boiler and the header or main, beyond the non-return 
valve. 

Check valves. Among these, the ball check is uncommon. The weighted 
check is more popular, as it can be used as a combination relief valve and 
check. The disk check has much the same bod)- as a globe valve and offers 
about the same resistance to flow. The swing check, by far the most com- 
mon, is simple, effective and oft'ers the least resistance to flow. 

A check valve is subject to severe service and must be so designed that 
its disk and seat can be repaired. In essential lines, such as boiler feed 
lines, a check valve should be protected by a stop valve on each side, so 
that a defective disk can be repaired without taking the pressure off the 
line. For feed lines to boilers in continuous operation, or when regulating 
valves are subjected to severe usage, both the check valve and the regulating 
valve should be protected by a stop valve on each side of the two ; the stop 
valves are normally wide open and are closed only when either the check 
or the regulating valve must be repaired. 

Combination stop and check valves are used frequently in boiler feed 
lines and can be combined with regulating valves to reduce the number of 
valves required to obtain a fair protection. 

In blozi'-oit connections, three types of valve are commonly used; a 
specially designed blow-off valve, a blow-off cock, and a gate valve. In the 
best practice a special blow-off valve and either a cock or a gate valve are 
installed in each blow-off connection between the boiler and the blow-off 
main, the cock or gate valve being located next to the boiler. The cock or 
gate valves should be opened first and closed last, when blowing down, so 
as to reduce the wear on them, and so that they can be depended upon to 
hold pressure when the regular blow-off valve is being repaired. Plug cocks 
are satisfactory- for this service, especially on boilers operated at low or 
medium pressures, but a gate valve is better and can more easily be used 
as a wash-out valve. Plug cocks should be equipped with a spring or other 
compensating device, to automatically take up wear. Steel or iron blow-off 
valves, gate valves and cocks should be extra hea\->-, steel being preferable 
for the higher pressures and temperatures. Valve disks and seats should 
be so arranged that thej' can be repaired. Blow-off service is severe and is 
particularly harsh when scale and sediment is present in quantity. 

The manufacturers have proposed that blow-off valves for power boilers 
operating with pressures up to 250 lb. be made onl}- in the extra heavy pat- 
tern and in the 1, \]2, 2 and 2^ i-in. sizes; the 1-in. size to be screwed, the 
V/z and 2-in. sizes screwed or flanged, and the IVz-'m. size flanged. 



PIPING 275 



Blow-Off Piping. Each boiler should have its own blow-off pipe. This 
should end in the boiler room, or where discharge on account of a leaky 
valve will be sure to attract attention. In most cities hot water is not per- 
mitted to be discharged into the sewer. A blow-off tank is then placed at a 
sufficient height that it will drain by gravity into the sewer. This tank 
should be provided with a man-hole, an open vent pipe, and with inlet and 
outlet pipes connected with the blow-off pipe and the sewer respectively. A 
valve should be placed in the outlet pipe. 

In horizontal return tubular boilers, the blow-off pipe should be covered 
with magnesia, asbestos or fire brick where it passes through the back con- 
nection. It can be protected by a connection from it to the boiler just 
below the water line. In this way, water is continually circulated, and the 
blow-off pipe will not burn. A valve should be placed in this connection, and 
closed before the blow-off cock is opened. 

Reference should also be made to Chapter 16 on OPERATION. 

Size of Steam Pipes 

ASIDE from the attraction of gravity, a fluid flows through a pipe only 
because the pressure at one end is greater than that at the other. The 
higher the velocity desired, the greater must be the difference between initial 
and final pressures. 

The problem of selecting a pipe to conduct a given quantity of steam or 
water in a given time therefore resolves itself into striking a balance between 
high velocity, which requires a high pressure drop but permits the use of 
a small pipe ; and low velocity, which requires a large pipe but can be 
obtained with a small drop in pressure. 

The drop In pressure caused by friction does not represent an equivalent 
loss of energy, because the energy reappears as heat. If the steam enter- 
ing the pipe line is wet, this heat tends to evaporate the moisture in the 
steam. If steam is dry when it enters the line, the heat tends to superheat 
it, or if it entered as superheated steam, to add to its superheat. The equip- 
ment to which the steam is delivered and in which it is used determines 
whether this heat, gained at the expense of a drop in pressure, is utilized or 
wasted. If it is utilized, the net loss due to friction is negligible; if not, the 
pressure consumed in overcoming friction becomes a loss. 

The use of a Iiigh velocity reduces the size of steam mains and thereby 
directly reduces the loss by radiation and the cost of the equipment. Steam 
velocities of from 3500 to 6000 ft. per min. have been common in the past, 
but in present practice velocities are from 12,000 to 20,000 ft. per min. This 
increase has occurred partly because superheated steam is being more com- 
monly used and also because prime movers utilize the superheat from pipe 
friction to reduce their steam consumption. Pipe friction represents an 
absolute loss if the steam consumption of an engine, pump or other apparatus, 
instead of being reduced because of the superheat, is increased because of 
the lower pressure. 

It has been determined analytically and experimentally that the pressure 
loss due to the steady flow of a fluid through a pipe of uniform diameter 
varies with the density of the fluid, is proportional to the length of the pipe, 
decreases as the diameter of the pipe increases, increases with the roughness 
of the interior surface, and increases nearly as the square of the velocity. 

The old method of basing steam pipe sizes on the velocity of the 
steam, has given place to the more correct method of determining the pipe 
diameter in accordance with the drop of pressure allowable. It is almost 
immaterial what the velocity may be so long as this pressure drop condition 
is met. 



276 PIPING 



The formula srenerallv used i; 



jr' 



{■--f) 



P = 0.000131 X ^~ ^. from which 

Tv' a 



v: = s; 



p (f 



^ .(..M) 



(18.) 



P =: Drop in pressure, lb. per sq. in. 
JV = Weight of steam flowing, lb. per min. 
Ji = Length of pipe, feet 
d = Internal diameter of pipe, inches 
ZL' = Mean density of steam, lb. per cu. ft. 

This formula, as simplified by Spitcglns (Armour Engineer. 1917). is 




where : 

If = Weight of steam in pounds per second 
P = Pressure drop in pounds 
zi' = Mean density of steam 
h =z Lenarth of pipe in feet. 
j^= 1100^ for 16 in. pipe 
800 for 14 in. pipe 
550 for 12 in. pipe 
350 for 10 m. pipe 
195 for 8 in. pipe 
97 for 6 in. pipe 
60 for 5 in. pipe 
32.5 for 4 in, pipe 
15.5 for 3 in. pipe 
8.5 for Il'o in. pipe 
5.1 for 2 in. pipe 
2,5 for V/2 in. pipe 
0.75 for 1 in. pipe 

GebJmrdt says that this formula (\9) gives results which accord closely 
with obser\-ation, and as it is more convenient to use than (18) it is to be 
preferred. To facilitate the determination of steam pipe sizes, the following 
charts: Figs. 147. 148, 149. 150 and 151. have been prepared in accordance 
with the above values of k as determined by S/'itcglas. Particular care 
has been taken to make them very easy to use. The following instructions 
will make this quite clear : 

Saturated Steam. 

1. Enter the lower left-hand scale with the weight of steam to be carried 
in pounds per hour, 

2. Proceed vertically to the proper curve of pressure, which is the 
initial pressure at the entrance of the pipe. 

3. From this intersection, proceed horizontally to the right to the curve 
of pressure drop per 100 feet. 

4. Proceed vertically downwards from this intersection to the lower 
right-hand scale and read the size of pipe required. 



PIPING 



277 




O 



(U 

e 

ID 
+-> 



C 
D 
O 

0. 

o 
o 
o 



(U 



w 






2n 



PIPING 




PIPING 



279 




u 

3 
O 

X 



a 

o 



c 

o 
£U 

o 
o 
o 

o 

o 



o 
o 
o 



(U 

a 



«4-l 

o 



N 









280 



PIPING 



_ _— - ^ 

„„....„... A.....A...A A 








- — Si^ i s ^ 


M.,..^..\...\ 


^ \ \ it 

m__\,1 4j,_„.-. 


S{L-^-\-V-- 


1 ..A--0\-V- 


. ^._^.^..\. 




. fg ""a^ 


PX& ^5r- ^^ 5 ^ § ^ ^ § 


+/(3i Li+-:iS '^ 5 '' »■ S * ^ 5 ? ' 


. Jr I'Z/.Vi^^''-';5^^^5^^'^'^"' 


-^ P^ii^^^"^' t^:^^^^'^^^^^^^'^ 


■i--^ ^ ^ "^ " ^■^''^''^?.^''''^^<?^^''' 


^^ l>^^ <■'' ^''.^x^ "^ v' ^ ■> Z' /" y* 


_ - " _ - -""--^Iq:^^^^::^^^ ^^^:<^^^^^ 


--=^" ^^^>^'^%^^:^^^/^^^ 


^^ -^^^"^ ^■^Z^z^'y A^^ 


^^"^ ^^^^OP' ^Zt^ ^^1^'^ /J7 


^^Z^^^t^^^ 2,^^ ^v^7 


- - - -^^'^^'^- ^B^I.^^ZZ/^ /.t^Z 


^-=^^ ^<q5^^C2 /*Z^ 


^^^ ^^^J^v^ /:-Z^ 


' ^^ ^^yrg^ ^ 2^^ 




-'^ ^ >n>f\o%> / 


' ,-^ ^^^ J;<t>yfw^ 


^^^^ ^ i^S^ 


^^%^ 7 -.^ /^ 


^ y^ -.Z ^ Z 


_ _,^ ^ _Z V / 


^ ^2 y'^^ 


y 7 ^ ,' 


' Z ^ ^ 


-.Z ^^^^ 


_ _ __ _ _ _z ^z_z 


z z 2 


' /^ / 


J y 


/J 


_ _ - _ - -^Z 


z 


/ 


r 








4- 












_j_ 


J 



53 






I 

^^ 

lis 



3 
O 



<u 



CO 



C 

o 

a. 

o 
o 

o 

o' 
o 
o 



o 
o 
o 

o~ 
o 



(U 

a 



<u 

N 
CO 



bi3 



PIPING 281 

SupcrJicatcd Steam. 

Enter the lower scale of Fig. 151 with the pressure at the pipe entrance, 
and proceed vertically upwards to the proper curve of the temperature of 
the saturated steam {not degrees of superheat ). Proceed from this inter- 
section horizontally to the right, and read the pressure found on the right- 
hand, scale. Now proceed as directed above for saturated steam, using as 
initial pressure the pressure just found from Fig. 151. 

The reason of this procedure is that the steam flow depends upon the 
average density of the steam, and Fig. 151 simply finds a pressure at which 
saturated steam has the same density as that of the superheated steam in 
question. 

To hnd the weight of steam per hour, divide the equivalent evaporation 
per hour by the factor of evaporation. Or multiply the B.H.P. by 34.5 and 
divide by the factor of evaporation. 

The pressure drop is for 100 feet of pipe, and the drop for any other 
length is in direct proportion. 

The drop of pressure per hundred feet varies in old installations from 
half a pound to five pounds. IModern practice allows two to four pounds 
pressure drop per hundred feet. The tinal result is governed in each instance 
by the smallness of pressure drop desired, modified by the cost of the pipe 
required to attain it. 

Formulas for the length of pipe with resistance equivalent to that offered 
by valves and fittings, give results that vary widely and are of little practical 
assistance. It is therefore customary to assume the following values for 
resistance : 

Obstruction Pipe Diameters 

Entrance of pipe 60 

90 deg. elbow 40 

Globe valve 60 

The resistance of long radius bends is assumed to be equal to the same 
length of straight pipe. The resistance of gate valves is considered negligible. 

In the steam flow formulas, the figure for density should represent the 
mean density of the steam in the pipe. The point of mean density may or 
may not coincide with the middle section of a given pipe, for if the fittings 
are numerous at or near one end and few at the other, the pressure drop 
and consequently the density will vary accordingly. For exact calculations, 
and for well insulated pipes, the change in density due to superheat by fric- 
tion should be considered. 

Size of Water Pipes 

Formulas for the flo-w of ivater in pipes are based upon the fundamental 
"*- hydraulic equation used in deriving the steam flow formulas, although the 
coefficient of friction is different. Gebhardt gives the following formula, 
credited to Cox, for the loss of head due to friction in water pipes : 

11 ..^^''+^''^^J^ (20 J 

1200 (/ 

// =: b'riction head, feet 

:' z= Velocity, ft. per sec. 

Ji =1 Length of pipe, feet 

(/ = Diameter of pipe, inches 

This formula applies only to the flow of water through clean straight 
cylindrical pipes of uniform diameter. The friction head caused by bends. 
\alves, fittings or ol)structions must be added to the friction head of the 
pipe, in order to determine the total head required to overcome friction. 



282 



PIPING 



aun^9auy tuod^^ ps^vjn^og 





\ 


' 


\\ 


\ 










































1 








\ 


> 


\ 


\ 


k 


\ 


\ 


















































\ 


N 


s. 


\ 


\ 




I 














































\ 


\ 


k 


\ 




\ 


\ 


\ 














































\ 


s 


\ 


V 


\ 


V 


V 


V 


\ 














































\ 




\ 


V 


k 


\ 


\ 


> 
V 


\ 










































\ 




\ 




\ 


N 


V 


\ 


\ 


\ 












































\ 




\ 




\ 


s 


s 


\ 


\ 


\ 








































V 




\ 




\ 




\, 


\ 


\ 






k 






































\ 




\ 




\ 


V 


s. 


\ 


\ 


^\ 






































V 


\^ 




\ 




^ 


s 


\. 


\, 


\ 


\ 


\ 








































N 


\ 




\ 


\ 


\, 


\ 


s 


V 


\ 


^^ 


\ 








































> 


\ 




\ 


V 


s. 


\ 


N 


\\ 


\ 












































\ 




\ 


\ 


s. 


\ 


\\ 


\ 


\ 












































\^ 




\ 


rs 


vV 


\ 


k' 


^ 












































\ ^ 


^ 


\^ 


s; 


kV 


\ 














































\ 


\ 


\J\ 


\ 


^ 


\ 












































\ 




\ 


> 


\N 




\ 


\ 












































\ 




\ 


A 


k\ 


\C 




^ 












































\ 


V 


\ 


.V 


1^ 






^ 














































S 


s. 


^^ 


\^ 














































' 


oA 


<^ 


^ 




s> 


V\\ 


^. 












































1 


f<^\ 


\ 


kN 


v\ 


hN 
















































"X 


\ 


N 


'Sb^^ 


N^ 




















































^ 


S 


vN\ 


S^ 




\ 
















































•^ 


fev 


\ 


\\ 


S^ 


\\\\ 


k 
















































•^ 


k 


\ 


S 


sm 


















































<" 


\ 


\ 




^ 


















































\ 






















































\\\^m 






















































N 


kxsnw^ 


























































\\^ 




















































^ 


iS^ 


^ 


























































\ 


^ 


^ 


























































^ 


J^ 


























































"^ 


























































> 
































































^ 



























































































































o^ 









10 



CO 
N 

a 



'•3 

c 
S 

CO 
u 
+J 
CO 

TJ 

+J 
CO 
u 

CO 

W 



s 

CO 

xn 

■M 
CO 

A 
u 

a 

CO 

4J 

t-i 
V 

> 

a 
o 
U 

ti 
.o 



u 

CO 

A 

u 



bfi 



PIPING 283 



The losses due to obstructions can be determined by: 

~2j (21) 



// = /.- ^' 



H = Friction head, feet 
k = Constant 
V ■= Velocity, ft. per sec. 
g = Acceleration due to gravity 
For the constant k, Gebhardt gives the following values : 

45 deg. ell 0.182 

90 deg. ell 0.98 

Gate valve 0.182 

Globe valve 1.91 

Angle valve 2.94 

The friction caused by valves and fittings can be expressed in terms of 
equivalent length of straight pipe ; the following values are used : 
Obstruction Pipe Diameters 

45 deg. ell 6 

90 deg. ell 30 

90 deg. tee 60 

Gate valve 6 

Globe valve 60 

Angle valve 90 

Bend, with radius equal pipe diameter.... 20 

Bend, with radius equal 2 to 8 diameters 10 

Water velocities in power plant practice range from 50 to 400 ft. per 

minute. The velocities in suction lines, especially in those carrying hot 

water, should be from 75 to 150 ft. per minute. A velocity of from 300 to 

400 ft. per min. is common in boiler feed lines. 

Expansion and Contraction 

THE expansion and contraction of piping because of temperature changes 
is large enough to demand careful consideration. Higher pressures and 
higher degrees of superheat emphasize the importance of the subject, as does 
also the increasing use of efficient insulating materials. Formerly it was 
assumed that radiation from the surface of a pipe reduces its expansion to 
about half the theoretical amount, but actual tests have shown that the 
expansion of well-insulated pipe closely approaches the theoretical value. 

The amount a pipe will expand depends upon its initial length, the rise 
in temperature to which it is subjected, and the coefficient of linear expansion 
of the material. This statement is expressed by the following formula : 

I = C h (h — t) (22) 

/ = Expansion, inches 

C = Coefficient of linear expansion, per deg. F. 
h = Initial length, inches 
t = Initial temperature, deg. F. 
ti = Final temperature, deg. F. 
The coefficient of linear expansion is not constant at all temperatures. 
In calculating the expansion of piping, the mean coefficient must be used. 
The coefficients of expansion of cast iron at different temperatures have th6 
following values : 

Deg. Coefficient 

100 0.00000600 

150 0.00000612 

200 0.00000625 

250 0.0O000642 

300 0.00000660 

400 0.00000700 

500 0.00000740 i 




X 



G 



CO 

s 

i2cQ 



ft. 



u 
OJ o 



05 



•:3 

ft. 



•I MM 



MiHa 




PIPING 



285 



The coefficient of linear expansion of other materials can be obtained 
by multiplying these values by 1.1 for wrought mild steel, 1.5 for wrought 
copper, and 1.6 for wrought brass. Table 30, due to Gebhardt, gives the 
mean coefficient of linear expansion of materials for different temperature 
ranges. 

Table 30. Coefficients of Linear Expansion of Piping Materials. 



Material 



Temperature 
Range 



Wrought iron and mild steel 

Wrought iron 

Cast iron 

Cast steel 

Hardened steel ^ . 

Nickel-steel, 36 per cent nickel 

Copper, cast 

Copper, wrought 

Cast brass 

Brass wire and sheets 



32-212 
32-572 
32-212 
32-212 
32-212 
32-572 
32-212 
32-572 
32-212 
32-212 



Mean 

Coefficient C 

per Deg. Y. 



. 00000656 
0.00000895 
0.00000618 
0.00000600 
0.00000689 
0.00000030 
0.00000955 
0.00001092 
0.00001043 
0.00001075 



Table 31. Increase of Length, in Inches per 100 Feet, of Steam Pipes. 



Temperature 










Increase, 


Cast Iron 


Wrought Iron 


steel 


Brass and Copper 


Degrees i 










50 1 


0.36 


0.40 


0.38 


0.57 


100 


0.72 


0.79 


0.76 


1.14 


125 


0.88 


0.97 


0.92 


1.40 


150 


1.10 


1.21 


1.15 


1.75 


175 


1.28 


1.41 


1.34 


2.04 


200 


1.50 


1.65 


1.57 


2.38 


225 


1.70 


1.87 


1.78 


2.70 


250 


1.90 


2.09 


1.99 


3.02 


275 


2.15 


2.36 


2.26 


3.42 


300 


2.35 


2.58 


2.47 


3.74 


325 


2.60 


2.86 


2.73 


4.13 


350 


2.80 


3.08 


2.94 


4.45 


375 


3.15 


3.46 


3.31 


5.01 


400 


3.30 


3.63 


3.46 


5.24 


425 


3.68 


L05 


3.86 


5.85 


450 


3.89 


4.28 


4.08 


6.18 


475 


4.20 


4.62 


4.41 


6.68 


500 


4.45 


4.90 


4.67 


7.06 


525 


4.75 


5.22 


4.99 


7.55 


550 


5.05 


5.55 


5.30 


8.03 


575 


5.36 


5.90 


5.63 


8.52 


600 


5.70 


6.26 


5.98 


9.06 


625 


6.05 


6.65 


6.35 


9.62 


650 


6.40 


7.05 


6.71 


10.18 


675 


6.78 


7.46 


7.12 


10.78 


700 


7.15 


7.86 


7.50 


. 11.37 


725 


7.58 


8.33 


7.96 


12.06 


750 


7.96 


8.75 


8.36 


12.66 


775 


8.42 


9.26 


8.84 


13.38 


800 


8.87 


0.76 


9.31 


14.10 



286 PIPING 

Approximate values for the linear expansion of steam pipes of cast iron, 
wrought iron, steel, brass and copper as given in Machinery's Handbook, 
will be found in Table 31. 

If the ends of a pipe were fixed and the pipe were heated, the tendency 
to expand would create a compressive stress. For the temperature changes 
common in power plants this stress would far exceed the compressive strength 
of the material. The axial force exerted by expanding or contracting pipe 
can be calculated as follows : 

P = C E A (h — t) (23) 

P z=z Axial force, pounds 
C = Coefficient linear expansion 
E = Modulus of elasticity 
A = Sectional area of pipe wall, sq. in. 
t = Initial temperature, deg. 
/j = Final temperature, deg. 
The moduh of elasticity of materials are as follows : 

Wrought iron 25,000,000 

Steel 30,000,000 

Cast iron 15,000,000 

Copper 15,000,000 

Brass 10,000,000 

According to this formula, a 6-in. extra heavy wrought iron pipe 200 
ft. long, if heated or cooled through a temperature range of 300 deg., exerts 
an axial force of 573,750 pounds. The sectional area of the metal of the pipe 
is 8.5 sq. in. so that the unit stress produced is much larger than the ultimate 
strength of the material. A temperature range of 300 deg. is by no means 
uncommon, so that for runs much shorter than the one assumed, piping must 
be free to expand or contract, and its expansion must be so controlled and 
directed that it will not strain connections, valves or fittings. 

Pipe Anchors 

THE expansion of piping cannot be limited, but its direction can be pre- 
determined by anchoring one end, both ends or the middle of a run. If 
one end is anchored, the expansion must be absorbed at the free end of the 
line. If both ends are anchored, the expansion will be from them toward the 
middle of the run and must be absorbed, preferably at some one place. With 
center anchorage the expansion is forced toward the free ends of the line, 
where it must be absorbed. 

Anchors must be firmly fastened to a rigid and heavy part of the power- 
plant structure, and must also be securely fastened to the pipe. If the pipe 
is not prevented from moving at the point at which the anchor is applied, 
the entire equipment for absorbing expansion is useless, and severe stresses 
will be thrown on all parts of the piping system. When both ends of a 
straight run are anchored with an expansion joint between, the end thrust 
is the steam pressure multiplied by the cross-sectional area of the pipe at its 
largest diameter. With sHp joints like Fig. 153, the area is that of the out- 
side diameter of the sleeve; and with corrugated joints as Fig. 154, or their 
equivalent, the largest inside diameter of the corrugations is to be taken. 
Thus, a 12-inch pipe with a slip-joint carrying steam at 250 lbs., will develop 
an end thrust of nearly 17 tons, and it may be greater than this with a 
corrugated joint. 

Expansion Joints 

"DlPE bends offer a satisfactory means of providing for expansion. The 
■^ radius of a bend should not be less than five pipe diameters. The pipe 
should be straight on each end for a distance equal to twice its diameter. 
Pipe bends should be fitted with extra-heavy lapped or welded flanges, be- 
cause the joints are subjected to severe stresses. Expansion is absorbed by 
a bend only because it is sprung out of normal shape, thus permitting the 
line to expand. 



PIPING 



287 






Fig. 152. Typical Pipe Anchors. 

Table 32, due to the Crane Company, shows the linear expansion pos- 
sible with quarter bends. The expansion values can be multiplied by 2 
for "U" bends, by 4 for single offset bends or "Expansion U" bends, 
and by 5 for double offset bends or circle bends. The values given do 
not take into consideration the springing of the bends when installing them. 
When a bend is sprung a distance equal to that in the table, twice the linear 
expansion given can be absorbed. 

Springing pipes when cold, so that they are then under tension, in- 
creases the linear expansion that can be cared for, and affords relief to lines 
used almost continuously at or near their maximum temperature. 





Table 32. Expansion (in Inches) Cared for by Quarter Bends. 




Size of 
Pipe, 
Inches 


MINIMUM 
RADIUS, IN. 


RADIUS OF BENDS, INCHES 


20 


30 


40 


50 


60 


70 


80 


90 


100 


110 




Standard 
Pipe 


Extra 

Strong 

Pipe 


120 


214 


10 
12 
14 


7 

8 

10 


3/8 

Vs 

5 

T6 


Vs 
11 

16 

Vs 


1 


2M 

VA 
IH 


3M 
2M 
2% 


43^ 

3^ 
3M 


5K 
4^ 

4^ 










3 


6 

5K 








SH 
















4 


16 
18 
20 


12 
14 
15 


'A 


7 
16 


15 
16 


ii^ 

1 -3- 

^ 16 


2^8 

IK 


23^ 
2H 


3% 
3^ 
3 


4M 
4K 
3K 


5M 

5K 

4^ 






4H 






5 


53/i 




6 

7 


26 
30 
34 


20 

24 
28 




y% 


9 
16 


1 


IK2 


2 

IK2 


23/2 

2M 

2 


3H 
2K 
2K 


4 

3K 
3 


4% 
4K 
3M 


5K 


8 






4K 










10 


45 
54 
70 


40 
50 

65 












1 


13/2 

1^8 
IK 


2 

IK 

IK 


2K 
2 


3 

2K 

2K 


3K 


12 








3 


14 




.... 




2K 



Table Z2> gives data as to minimum allowable radius and length of 
tangent, useful in laying out expansion bends. The illustrations annexed to 
the table show different designs. 

Expansion joints are of two general types. Slip joints consist primarily 
of a brass sleeve, sliding in a stuffing box. They are made with and without 




a 



CO 



CO ^ 

.2 S 
"S 'C 



go; 

u- CN 

o 

c 
o 

'5 

CO 



CO 

CO 

o 



PIPING 



289 






V 

a 

(L) 
-4-) 

0) 

a 

OS 
O 0^ 

S u 
3 2 
.2 

C 

a 



CO 

H 



:^ ^ 



CN 


-t 




00 On 

l-H 


C^l 




1 «S rn 


CN CN 

fO CO 


00 ON O 
■<-l CN 

1 


o 


c 


o o 

^-H 1—1 


00 00 00 1 

■«— 1 1-1 


00 


00 

c 

o 
00 


O 00 
CN 00 


00 00 00 

1— ( T-l 




ID 

1— 1 


O 00 
00 t^ 


OO 00 O 
1-H 1—1 








tH 1—1 




T— 1 


c 


O to 


V0 1>- -^ 

1—1 1-H 




o 


lOiO 


1—1 •rH 


o 

^—1 


o 


lO o 


CN t^ C 

1—1 1—1 


On 
OO 






1— 1 \0 Cn 

1—1 


c 


Tf 00 
fO CN 


On ^O OO 


"in 




CO CN 


00 ^ OO 


c 

CO 
CM 


\0 o 

CN CN 


t-^ vO l>- 


O to 

CN -H 


O to t^ 




CN 
CN 


00 ^ 
1—1 1—1 


NO to NO 


re 


c 

T— 1 


O CM 

■r-l 1—1 


to lO nC 


1—1 T— 1 


to to NO 


fC 




CN OO 


-+ to NO 




CN 
T. 

X. 

c 

1— 1 

"o ; 

00 . 

'^ '. 

fii : 

a; • 

^ ; 

C3 . 
c« . 

"> • 

-o • 

< : 
S : 
£ : 

1 '^ 


■»— 1 


Size of Pipe Inches 


CD X 

u o 

HH 1— 1 


c/2 CD 

O i, 

C C 

c 


T 

C 

c 

c 

c 
c: 
u 


- 


22 ^ • 
3 d. - 

"^ ^ r^ 
»S O CvJ 




i: 

c 

4-1 

c 


c3 
C 
0) 

:Q 



4-1 

1- 






290 



PIPING 



anchor bases, and with traverses up to about 10 inches. In the second ty^pe, 
expansion is cared for by the axial spring of a corrugated copper pipe. 
For high pressures, the copper is re-enforced by inner and outer iron equaliz- 
ing rings. Both t}'pes are useful when lack of space prevents the use of pipe 
bends. 

Fig. 153 illustrates the Ross expansion joint, showing the guide for 
maintaining the pipes in alignment. 




Fig. 153. Ross Crosshead Guided Expansion Joint. 

The piping between the anchors should be carefully lined up so that 
there will be no tendency for it to spring or buckle if the slip joint is too 
tightly packed. Bolts are necessary to prevent the sleeve being drawn out 
by such circumstances as the failure of an anchor. 

Fig. 154 is the Badger corrugated copper expansion joint, showing the 
reinforcing rings which lie in the corrugations and relieve the copper pipe 
of carrying the pressure. 




Fig. 154. Badger Self-Ekjualizing Expansion Joint. 



PIPING 



291 



The number of corrugations is dependent upon the amount of expansion 
to be absorbed. 

2 corrugations take care of 1 in. expansion. 

3 corrugations take care of 1>'2 in. expansion. 

4 corrugations take care of 2 in. expansion. 

The advantage of this type of joint is that no packing is required. 

Double-swing fittings are satisfactory for small piping in short runs, but 
not for heavy pipes or long runs. For a really good expansion joint, the 
threads of the screwed connections should be carefully cut and then ground 
in. It is hardly to be expected that a screwed connection can be^ steam- 
tight, and at the same time permit easily any movement in fitting the pipe. 

Szvivel Joints are similar to the double-swing screwed fittings, without 
the disadvantage of the latter. They can be used for lines containing flanged 
fittings, or when pipe bends cannot be installed. 




(brt^ 







c^ 



Q^^dD^O 




JUL 





Fig. 155. Three Classes of Pipe Supports — Hangers, Standards, andBrackets. 




c 

(S 

a 
U 

u 
IS 



S 



•-* o 






— m 



^1 



^ 3 



Q 






PIPING 293 



Flexible metallic iubiiig is excellent for absorbing expansion in small 
pipes. Care must be taken that it is not subjected to thrust or tension. It 
must be arranged in the same manner as Pipe bends just described. 



Supports and Hangers 

T)lPE supports and hangers vary of necessity with the plant layouts, but 
-^ their construction is fairly well standardized. Pipe supports, Fig. 155, 
can be divided roughly into three classes, — hangers, standards and brackets. 
Hangers are used for supporting piping from ceilings and overhead structural 
members ; standards for supporting piping on and from engine and boiler 
room floors ; and brackets for supporting piping on and from walls and 
vertical structural members. 

The plainer and lighter types of pipe hanger can be used for short runs, 
with steam or water lines up to about 6 in. diameter. On long runs they 
can be used if the connection between the hanger ring and the ceiling is long, 
and if its upper end is not rigidly attached to the ceiling. 

For large pipe, long runs or when the supporting strap must be short or 
rigid, the hanger should be equipped with one or more rollers. The support 
for high temperature lines should be equipped with a lower roller and also 
with a roller resting on the top of the pipe. The upper roller should be 
bolted by tie-rods to the support. Springs should be placed between the sup- 
port and the rods, so that the latter can move slightly. Supports for large 
or heavy mains should be adjustable to maintain alignment. 



Steam Separators 

I 'O protect plant equipment and obtain economical operation, all piping 
-'■ systems should be provided with separators to eliminate entrained mois- 
ture, condensate oil, grease or other foreign matter. Moisture carried into the 
steam cylinder lessens the economy in steam and lubricants, and may also 
cause damage. Oil in exhaust steam fouls the condensate, lodges in condensers, 
accumulates on turbine blades, and on the inner surfaces of radiators, and 
renders the condensate unsuitable for boiler feed. 

The function of a steam separator is to deliver clean, dry steam. Steam 
separators are used on live and superheated steam lines. The oil separator 
extracts the grease, leaving a condensate that is pure distilled water and 
therefore suitable for boiler feeding or for industrial processes. Oil 
separators are used on exhaust and vacuum steam lines, for low pressure 
turbines, feed water heaters, condensers and heating systems. 

Steam and oil separators operate either by intercepting the steam cur- 
rent, or by changing its direction. Cast iron bodies having various shaped 
grids in the form of single or multiple baffles are ordinarily used for 
separators. The accumulated matter is drawn off intermittently or is taken 
care of continuously by a trap. 

The separators. Figs. 156, 157 and 158, are practical designs intended for 
vertical, horizontal or angle pipe connection, A single, ribbed baffle has a 
steam port at each side ; below it is the collecting well with its water gage 
column. Steam entering from one end of the pipe line impinges on the 
baffle, where it leaves the water or oil, and continues on around either side 
of it, through the steam ports. The intercepted water or oil is directed, 
by the ribs' on the baffle, down to the well. A drain, to catch any con- 
densation, is also provided on the "dry" or steam outlet side. 



294 



PIPING 





Fig. 156. Horizontal and Vertical Steam Separators. 



m 







=] 



Fig. 15 7. Horizontal and Vertical Oil Separators. 



PIPING 



295 



The receiver type separators, Fig. 158, are usually made of plate and 
may have riveted or welded joints. This construction is used when long lines 
of piping might be subject to violent vibration. The large receiver serves 
as a reservoir for steam and is useful to supply the intermittent demand of 
a slow speed engine, and receives any inrush of water from the main. The 
water in the receiver is stored until a trap drains it away. The steady flow 
of steam resulting from the installation of a receiver separator often makes 
possible the use of smaller mains, which decrease the first cost, and reduce 
the loss of heat by radiation. 






Fig. 158. Horizontal and Vertical Receiver Separators. 



All separators should be selected on a basis of the steam supply required, 
and not by the size of the flange or pipe outlets. 







c 

6 









K 

T. ■"■ 

a: _ 



S -r 



297 



CHAPTER 9 



AUXILIARIES 

Quantity of Feed Water 

THE quantity of feed water required per hour is the B.H.P. to be devel- 
oped, multiplied by 34.5, and divided by the factor of evaporation. To 

allows some margin, the division by the factor of evaporation is omitted. 
As there are 8.3 lb. of water to the gallon, the rate becomes 4.15 gallons per 
hour or 0,07 gal. per minute. This hgure, expressed as 7 g.p.m. per 100 
E.H.P., is frequently used in determining pump sizes; but it is too small. 

Boilers are often run at considerable overloads for long periods. There- 
fore, the quantity of feed water required must be based on the probable 
B.H.P. to be developed, and not on the boiler rating. As the demand for 
feed water fluctuates with the load, the supply must be large enough to take 
care of peak loads. Pump makers allow from 7^ to 10 g.p.m. per 100 B.H.P. 
developed to take care of contingencies. 

The feed pump must not only overcom.e the steam pressure in the boiler, 
but must also develop a head sufficient to overcome pipe friction in the 
system, the resistance of the feed check valves, and some excess pressure 
besides. Therefore the feed pump must usually discharge at a pressure 
of 25 to 30 lb. in excess of the boiler pressure. 

Direct-Acting Steam Pumps 

TDUAIPS are divided into three general types: direct-acting steam pumps, 
■^ centrifugal pumps, and positive displacement power-driven pumps. 

The popularity of the direct-acting steam pump as a boiler feeder is 
due in great part to the fact that it is the oldest and best known type. Often 
it is the only type of pump well understood by the operating engineer, and so 
represents the only good solution to the feed problem. 

For feed purposes the simple steam end is generally used. It is not so 
economical of steam as the compound or triple expansion steam end, but the 
latter cost so much more that only rarely are they selected. The greater 
number of parts with the complication and extra space are also against the 
compound and triple pumps. 

Tables 36 and Zl show the economies of steam-turbine-driven centrifugal 
pumps and the direct-acting steam pump. If the plant layout does not provide 
an excess of exhaust steam for feed heating, or other useful work, the 
exhaust steam from the pump can be thus used to increase the thermal 
efficiency of the plant. On the other hand, if the exhaust steam has to be 
wasted to the atmosphere, the economy of auxiliaries becomes important and 
the direct-acting feed pump is often displaced by a more efficient type. The 
pump that gives the average water horsepower for the least expenditure for 
coal is the one to be desired, therefore the great difference in the steam 
consumption of direct-acting pumps and centrifugals, in the larger sizes, 
eliminates the former from consideration. 

The centrifugal pump is not suited to the smaller capacities, so that the 
direct-acting steam pump finds one of its most useful fields in installations up 
to 2,000 boiler horsepower, in which a compact steam pump is desired. Its 



298 



AUXILIARIE S 



chief competitor in this capacity range is the motor-driven triplex pump, but 
owing to the lower cost and greater ease with which steam can be supplied, 
the steam pump is often preferred. Above 2000 boiler horsepower the cen- 
trifugal pump is usually favored. 

Direct-acting steam pumps can be classified as to the number of steam 
and water cylinders, that is, simplex or duplex, one steam and one water 
cylinder, or two of each side by side. 

Simplex pumps are often preferred for boiler feed service because the 
design always insures a full, complete stroke. When the pump cannot "short 
stroke," the piston rods, cylinder liners and plungers cannot wear down in 
the center, leaving a shoulder at each end. These shoulders may cause 
sticking of the pump or breakage of the cylinder or stuffing boxes due to 
the wedging effect of the "shouldered" portions, when the stroke is unex- 
pectedly long or full. 

Another advantage of the simplex pump is that it has only about half 
as many working parts as has a duplex pump. Consequently fewer parts 
wear out and fewer spare parts need to be carried. This applies particularly 
to the water valves. 

The simplex pump has but one water piston. Even if this is double act- 
ing, a steady and uniform flow of water from the pump is precluded. The 
steam valve-gear always reverses quickly at the end of the stroke, but there 
will still be some pause at this point. A break in the flow of the water 
results, sometimes developing a water hammer in the discharge lines. Sim- 
plex pumps should be equipped with a generous sized air chamber on the 
discharge line. The chamber must always be kept well filled with air to 
act as a cushion and to compensate for that absorbed by the water. 



Table 34. Ratings of Simplex Direct-Acting Steam Pumps. 



SIZE 


Single 

Strokes 

per Min. 


Double 

Strokes 

or R. P. M. 


Capacity, 

Gallons per 

Min. 


Boiler Hp. 

(34H lb. 

Water per Hr.) 


Piston 

Speed, 

Ft. per Min. 


3x2x4 

4^x33^x6 

53^x31^x7 


57 
50 
49 


28.5 

25 
24.5 


3 

7.5 
12.2 


50 
110 
175 


19 

25 
25 


6x4x8 

73^x5x10 

9x6x12 


48.6 

48 

42 


24.3 21 300 
24 40 580 
21 j 61 870 


32.5 
40 

42 


10x7x12 

14x8x12 


42 21 
42 21 


84 
109 


1,220 42 
1,570 42 



Table 34 gives the usual commercial sizes of simplex pumps and their 
normal ratings for boiler feed service. Under the heading "size" the three 
figures indicate the diameter of the steam and water cylinders and the length 
of the stroke. The sizes and ratings are the average prevailing among sev- 
eral of the prominent pump manufacturers. Some pumps, by virtue of large 
valve areas and water passages, are rated for greater boiler horsepowers 
than others of the same dimensions. The factor of safety may differ, thus 
affecting the rating. The sizes given indicate the usual range for this type 
of pump. The simplex pump is most popular in the smaller sizes, as the pul- 
sating discharge effect is magnified in the larger sizes. 

The rated capacities, in Tables 34 and 35, are based upon a volumetric 
efficiency of from 85 to 90 per cent. The efficiency attained in the boiler 
room depends upon the care taken of the pumps, and probably will not ex- 
ceed 60 to 65 per cent. This is equivalent to realizing a capacity of about 



AUXILI ARTE S 



299 



70 per cent of the boiler horsepower given in Tables 34 and 35. The pump 
should then be of a size so that it can gain on the largest load likely to be 
carried, or so that the water level can be raised during a peak load if it 
has fallen too low, without racing the pump. 

When hot water is handled the piston speed is from one-half to one- 
third of what would be good practice for pumping cold water. This is to 
prevent vaporization of the water and keep the pump from becoming "steam 
bound." If the piston speed is too high, the water will not follow the 
piston or plunger during the suction stroke, and a partial vacuum is formed 
in the plunger chamber. When the plunger is reversed it travels quickly 
through the vacuous space created and meets the water with an impact suffi- 
cient to cause a serious knock. The pump then vibrates badly and the knock 
may even damage the water valves or other parts, as well as the pipe lines. 

The duplex pump (two water cylinders) discharges the water at a much 
more uniform rate of flow than the simplex type, as the steam valve gear 
of one side is actuated by the piston on the other side of the pump, and 
the steam valves are so designed that the two pistons are 90 deg. apart in 
the working cjxle. Generally both water pistons are moving. At the end 
of the stroke of one piston, during the slight pause, the other side is working, 
thus maintaining a more even water flow than is present in a simplex pump. 
In operating these pumps both sides should have a "full" stroke, or the cylin- 
ders or stuffing boxes may be broken through the shoulders formed when 
"short stroking." 
. Table 35 gives the prevailing sizes and ratings of duplex pumps. 

Table 35. Ratings of Duplex Direct- Acting Steam Pumps. 





EACH SIDE 


Capacity, 

Gal. per 

Min. 


Boiler H. P. 

(34 3^ lb. 

Water per 

Hr.) 




SIZE 


Single 
Strokes 
per Min. 


Double 

Strokes 

or R. P. M. 


Piston 

Speed, 

Ft. per Min. 


3x2x3 

43^x2^x4 

5^x3^x5 


72 36 
57 ! 28.5 
53 1 26.5 


5.7 
11.4 
21.5 


95 
190 

360 


18 

19 
22 


6x4x6 

73^x5x6 

73^x43^x10 


50 
50 

49 


25 
25 

24 


32 
50 
65 


535 

840 
1,080 


25 
25 
40 


9x534x10 

10x6x10 

10x7x10 


48 
48 
48 


24 
24 
24 


87 
116 
156 


1,450 
1,940 
2,600 


40 
40 
40 


12x7x12 

12x81^x12 

16xl0%xl2 


42 
42 
42 


21 
21 
21 


164 
243 
370 


2,750 
4,050 
6,200 


42 
42 
42 



Piston pumps, or those having water pistons operating inside the water 
cylinder, and packed to a good fit, are necessarily more subject to water 
slippage or leakage past the pistons than is the plunger type, in which the 
leakage is through a stuffing box to outside the pump. In the plunger type 
the packing in the stuffing box can easily be adjusted to care for any leakage 
that develops due to wear. In the piston type the adjustment of the pack- 
ing in the piston, if there is any, necessitates partly dismantling the pump. 
This is so troublesome as to be often neglected. The fact that the leakage 
cannot be easily detected renders this type unsuited to high pressure work, 
since the leakage increases with the pressure. 




s 



'^ ^ 

C (0 
O 4J 
4-. W 
n 



u o 
o o 

U 

Q c 

o 



tH 



::^ O 



.Sm 



"5 ,5 

CO u 
T3 as 

5 " 

CO u 

a 

(/3 



W 



5 o 

CU CO 

w c 

^ OS 



A U X T L I A R T E S 301 

Although wear of the plunger can be easily detected, ihc plunger is 
easily scored from dust and grit. Also plunger pumps cost more than the 
piston t\-pe so that the}' are used principally for tlie higher pressures. Piston 
pumps are not used for water pressures over 150 to 200 pounds. The plunger 
type is preferred where the pressures are in excess of 150 pounds. 

Hot water has a corrosive effect upon iron, especially when it travels 
over the iron surface at velocities such as are present in a pump. It is well 
therefore to preserve the pump by making certain parts of brass or bronze. 
The water cylinder should have a brass liner, and the piston should be bronze 
or brass. The water valves can be of bronze or hard rubber, with bronze 
seats. The water piston, rod, or plunger, can be of iron or steel. Iron 
plungers are usually preferred, especially in the larger sizes, but unusual 
water conditions often dictate the use of bronze, even at a considerable in- 
crease in cost. 

The performance of simple direct-acting steam pumps can be calculated 
from the following formulas : 

I-LP.^^IL (24) 

3960 ^ ^ 

d- G 
^=^ (25) 

M.E.P.=/' (P—BF)=().7i) (P—BP) (26) 



M.E.P. d' 



Kl?) 



H =: Discharge head, feet 

H'=:Head, feet 

H" = Head, pounds 

G = Capacity, gal. per min., double acting pumps only, either 
simplex or duplex 

5" = Piston speed of pump. ft. per min. (for one side only of 
duplex pump) 

d =z Diameter of plunger or water piston, inches 
D = Diameter steam cylinder, inches 
H.P. = Delivered or water horsepower 

k =z Constant =: 5 in. for simplex pumps 
= 3.55 for duplex pumps 
M.E.P. =z Mean effective pressure in steam cylinder 
P = Steam pressure at throttle, absolute 
BP:=: Back or exhaust pressure, absolute 
F =: Diagram factor = 0.70. 

Direct-acting pumps must be large enough to feed the boilers when 
operated at normal or slow speeds. A high speed direct-acting pump hand- 
ling hot water may ''knock" badly and cause damage to the discharge pipe 
lines. 



302 



AUXILIARIES 



Table 36. Steam Consumption — Simple Direct- Acting Steam Pumps. 
In pounds per water horsepower per hour. 



Stroke. 
Inches 



>teani Pressure at Pump, Pounds Gage 



60 



SO 



90 



100 



110 



120 



130 



140 



150 



4 


230 


210 


204 


200 


195 


190 


188 


187 


186 


6 


200 


170 


165 


162 


158 , 


156 


154 


153 


152 


8 


160 


145 


142 


139 1 


137 1 


135 


134 


133 


132 


10 


140 


130 


126 


122 


120 ! 


119 


117 


116 


115 


12 


130 


120 


116 


112 


110 


109 


108 


107 


106 


15 


120 


110 


106 


104 


102 


100 


99 


98 


97 


18 


100 


104 


100 


97 


96 


94 


94 


93 


92 



Table 36 gives the steam consumption of the simple pumps used for 
boiler sen'ice. Some designs will be more efiicient than others, so that 
the table will not apply to every simple direct-acting boiler feed pump. The 
values are for pumps in good condition, with a well lagged steam cylinder, 
receiving drj- saturated steam at the throttle, and exhausting to the atmos- 
phere. 



Centrifugal Pumps 

^^^ENTRIFUGAL pumps are compact, practically noiseless, require small 
^■^ foundations, and pump at practicalh' a uniform rate. They require little 
lubrication or adjustment of packing. Once started, they can be left without 
attention for a considerable time. 

These pumps are most in favor for the larger installations, in which the 
boiler capacity is 2000 horsepower or more. The running clearance inside the 
pump is small, at points where the water under discharge pressure is sep- 
arated from the suction side, so that slippage must be considered. Many 
ingenious devices are used to reduce this leakage and to ser\-e as a correc- 
tion when it does occur. The clearances cannot be reduced enough to elimi- 
nate slippage, so that the capacity and hence the loss in small pumps is 
proportionately greater than in the larger ones. The larger sizes therefore 
give the best results. 

Centrifugal feed pumps are usually of the multi-stage t\-pe, each stage 
doing its proportionate part of the work of increasing the water pressure. 
The maximum pressures are from 60 to 100 lb. per stage. Thus a 250-lb. 
discharge pressure would mean a three-stage pump. The water is received 
by the first-stage impeller, which picks it up and imparts to it a velocity head. 
This velocity is reduced, either in a channel of gradualh" increasing area, 
or in a diffusion ring having vanes and passages, while the water is conducted 
to the impeller of the next stage. 

The head developed depends upon the velocity- imparted to the water, 
and will therefore be governed by the peripheral velocity- of the impeller. 
Thus for a given head there can be used either a large diameter impeller 
with a slow rotative speed or a smaller diameter and proportionately in- 
creased R.P.M., to give the same rim speed. As the diameter of the ira- 



AUXILIARIES 



303 



peller governs the diameter of the pump it is desirable to have high speeds, 
with smaller impellers, to reduce the cost and the space required. 

For ordinary, or small changes, the capacity of a centrifugal pump 
varies directly as the speed, and the head as the square of the speed. This 
applies particularly for maximum efficiency at the different heads. 

The operating characteristics of a well designed feed pump are shown 
in Fig, 159. The curves are laid out so that heads, capacities and speeds are 
expressed in percentages. Thus if 500 g.p.m. is the normal capacity it will 
be shown as 100 per cent on the capacity scale ; 250 g.p.m. will be given 
as 50 per cent ; and 625 g.p.m. as 125 per cent of normal. 



80 >- 




) 10 20 30 
Fig, 159. Operating Characteristics of Centrifugal Pumps. 



40 50. 60 10 &0 90 100 110 120 130 140 150 160 
Percent of Capacity at Maximum Efficiency Point 



The heavy lines show the head, capacity and characteristics for normal 
speed operation and the lighter lines the performance at fractional speeds. 

As boiler feeding takes place practically at constant pressure a change 
in capacity must be met by a change in speed or by throttling. Hence the 
head can be considered as fixed, and can be indicated as 100 per cent or the 
Line "A." 

The head-capacity lines for different speeds cut the line "A" at points 
indicating the percentage or normal speed for the capacities at this head. 
The brake horsepower capacity lines will then show the percentage of normal 
horsepower for different speeds. Maximum efficiency lines give the actual 
pump efficiency for any head and capacity. These also are based upon 
percentages. 

As an example, take a pump designed for 400 g.p.m., 200 lb. pressure, 2600 
r.p.m., 62 per cent efficiency, and 75 brake horsepower required for driving. 
All these are represented by 100 per cent on the curve. Suppose it is desired 
to find the other conditions for a capacity of 300 g.p.m. Then say — 
Capacity = 300 g,p.m. /^given) = 75 per cent of normal 
Head = 200 lb. =: 100 per cent of normal (no change) 
Speed == 96 per cent of normal (from curve) =: 2500 r.p.m. 
Efficiency = 96 per cent of normal (from curve) = 58.5 per cent 
Brake horsepower = 80 per cent of normal (from curve) = 60 brake 
horsepower. 




Kimball Building, Chicago. 111., equipped with Heine Standard Boilers. 



AUXILIARIES 



305 



Fig. 159 shows the relations upon which depend the regulation of the 
pump to meet varying demands. The head-capacity curves give the best 
information as to the operation of centrifugal pumps. The efficiency curve 
should be flat, so that the efficiency is high over a wide capacity, thus main- 
taining good economy under speed regulation. 

The horsepower curve should rise to a maximum at the normal operating 
capacity and then fall off so that no overload vi^ill be thrown on the driver 
should the pressure be reduced. This is particularly important in motor 
driven pumps, since overloads can be serious. 

Table Z1 gives capacities and steam consumption for different sizes of 
centrifugal feed pumps. The calculation of capacity is explained elsewhere. 

Table 3 7. Performance of Three Stage Centrifugal Feed Pumps. 
(150 Lb. Steam Pressure — 175 Lb. Water Pressure — 13 5 Ft. Per Stage) 



Size, 
Inches 


R. P. M. 


G. P. M. B.H.P.* 


Pump 

Effic. 

Per cent 


H.P. 
Req. 


Turbine 
Water 
Rate, Lb. 
per Brake 
H.P per 
Hr. 


Steam, 

Lb. per 

Water 

H.P. per 

Hr. 


3 

4 

5 


2,500 to 3.000 
2,600 to 3,000 
2,200 to 2,730 


300 

500 
750 


4,000 

6,700 

10,000 


56 
64 
67 


53 

78 
110 

140 
210 


42 
42 

42 

39 
38 


75 
66 
63 


6 

8 


1,500 to 2,000 
1,500 to 2,000 


1,000 
1,500 


13,200 
20,000 


70 

71 


56 
54 



* 0.075 gal. per B.H.P. used to provide a factor of safety. 

The turbine water rates represent commercial averages. The column at 
the right (steam per water H.P. per hour) is given so that the performance 
can be compared directly with that of direct-acting steam pumps. 

Performance data, due to /. Brcslav, are given in Table 38 for a boiler 
feed pump and for a compouna duplex direct-acting steam pump. Both pumps 
were designed for 250 g.p.m. and were operated nine hours a day at 160 lb. 
steam pressure and 2 lb. l^ack pressure. 

Table 38. Operating Cost Comparison of Boiler Feed Pumps. 

Turbo Comp. 
Centrifugal Duplex 

First cost $1,008 $980 

Valves to be watched 14-18 

Packing boxes 4 18 

Oil used in 15 days, pints .A.bout 4 30 

Grease, pounds 4 

Maintenance, packing, etc.. per year $30 $120 

Steam consumption, pounds per boiler horsepower per hour 38-40 40-55 

A simple duplex steam pump would have cost here about $600 but the 
steam consumption would then be about ICX) lb. per B.H.P. per hour. The 
comparison shows that the compound steam end type of a direct-acting 
pump is required, if the economy of the turbine driven centrifugal pump is 
to be obtained. The direct-acting pump is more complicated however, and 
the maintenance and lubrication charges are much greater. 

The leading advantages of centrifugal pumps are compactness, silent 
running, durability and superior economy in cost of power, attendance and 
repairs, and the facility with which they may be adapted to any location 



306 



AUXILIARIES 



where they may be supplied with power by direct connection to an electric 
motor or steam turbine. As boiler feeders, they have the advantage over 
reciprocating pumps of continuous delivery without shock or hammering, and 
of producing no excessive pressure on feed mains for any adjustment of 
feed stop valves or other stoppage of pipe connections. 

The commercial forms of centrifugal pumps are usually of the multi- 
stage tv-pe, either with or without diffusion rings. 




Fig. 160. De Laval Turbine Driven Centrifugal Boiler Feeder. 



Fig. 160 shows a pump without diffusers. The water after being picked up 
by the impeller of one stage is discharged to the next stage through a return 
channel cast as a part of the pump casing. This channel is designed so as 
to reduce gradually the velocity- of the water leaving the impeller and trans- 
form this velocity' to pressure head. The advantages of this type of pump 
are said to be simplicity of construction and the absence of small water pas- 
sages that might become blocked by foreign matter. 

A single stage direct turbine-driven centrifugal feed pump has attained 
some favor in Europe and is also beginning to be recognized in this countrj-. 
This has a pump impeller and turbine wheel mounted on one short shaft. 
The pump and turbine housings are close to each other and as the machine 
runs at a high speed, 5C00 to 8000 r.p.m., it is a compact unit. These pumps 
are designed to produce sufficient pressure to feed any usual boiler, and can 
operate against a pressure of 250 lb. or greater. Owing to the high speed, 
this pump is not accepted for general boiler feed use in this country, in 
spite of its low cost and the small space required. 

When the water is fed through an economizer to the boiler a four-stage 
pump can be arranged so that one stage pumps to the economizer and 
through it lo the main feed pump, which has three stages and discharges 
into the boiler. Sometimes the pumping unit is made up of two separate 
pumps, each with its own driver; but two pumps on one base, and driven 
by one prime mover, are to be preferred. Thus each pump always works in 
harmonj- with the other. The two pumps can be arranged, with the econo- 
mizer stage uncoupled or by-passed, to feed directly to the boilers. These 
economizer sets are particularly well adapted to plants in which it is de- 
sired to decrease the water pressure in the economizer tubes, because the 
pressure in the economizer is usually one quarter of that with the ordinary 
feed pump. 



A U X T L T A R T 1^: S 



307 



Fig. 160a shows a multi-stage high-pressure centrifugal pump used for 
boiler feeding. It is really a volute pump so arranged that the volute of 
one stage is led into the suction of the next stage, and the high pressure is 
attained by putting in series as many stages as necessary. It is claimed that 
the advantage of the volute, besides the simplicity, is that the efficiency is 
maintained for a greater range than with the diffusion vane type of pump ; 
also the cost of the diffusion vanes, which are subject to wear, is eliminated. 
The force on the horizontal split of the case, due to the high pressure of 
the water, is taken care of by the bolts on the outside flange, and by through 
bolts nearer the center line. The hydraulic balancing mechanism, which per- 
forms the functions of a thrust bearing, is so arranged that both stuffing 
boxes are under a low pressure and sealed with water. Every part of the 
pump, except the case and shaft, is made of bronze. The two ring-oiled 
bearings are equipped with large oil reservoirs. 

Turbine-driven centrifugal boiler feed pumps have many advantages in 
addition to their compactness and reliability. 




Fig. 160a. Lea-Courtenay Multi-stage High-pressure Centrifugal Pump 

for Boiler Feeding. 

They give reliable and uninterrupted service with little, and often un- 
skilled, attention. 

There is an entire absence of pulsation, shock, vibration or over-pressure 
in pipe lines, thus making relief valves unnecessary and rendering the 
pump suitable for use with automatic boiler feed regulators acting inde- 
pendently at each boiler, or with feed-water meters. 

The cost of maintaining the piping system is reduced, because less strain 
is thrown upon it. 

Close governing is obtained, either at constant speed or at constant 
excess pressure. 

There is entire freedom from liability to injury by overloading. 

Troublesome parts, such as valves, packings, sliding surfaces, air chamber, 
etc., are eliminated. 

There is little expense for attendance and upkeep, due to the simplicity 
and few wearing parts. All parts are easily accessible. 

Cylinder lubricants are not required and little oil of any kind. 

The steam consumption is lower than that of direct-acting pumps, and 
superheated steam or low pressure steam can be used. 

The exhaust is entirely free of oil and can be used in open feed heaters, 
or introduced into an intermediate stage of the main turbine without danger 
of introducing oil into the boilers. 



308 




3 
N 

> 



C 
OS 
u 

o 

V 

C 

V 



o 
U 

B 

3 
«> 

"o 

u 



as 
O 



o 



OS 

c 

CS 

CO 

.2 
*S 

M 



» 



AUXILIARIES 309 



Direct-Acting Power Pumps 

DIRECT-ACTING power pumps are rarely used for boiler feeding. These 
positive displacement pumps are selected usually where the available 
sources of motive power prevent the use of the direct-acting steam pump. 

These pumps are reliable, their maintenance cost is low and in small 
capacities their efficiency usually higher (lower brake horsepower required) 
than centrifugal pumps. 

In the larger sizes, 3000 boiler horsepower and over, they become ex- 
pensive and the centrifugal pump is more generally used. 

The triplex plunger pump gives a steady flow of water, the cost of power 
is less than the centrifugal pump when applied to boiler feeding, it can be 
automatically regulated, it is reliable and if given intelligent attention it will 
maintain its high efficiency for 15 to 20 years with, no cost for repairs ex- 
cept for packing and valves. 

The high efficiency of the triplex pump is attained not merely at its 
rated capacity, but is nearly constant throughout the full range of operation 
provided its capacity is regulated by changing the speed. The average effi- 
ciency is therefore greater than a mere comparison of catalog percentages 
would indicate. 

The triplex pump has a practically constant efficiency at different speeds. 
The capacity is proportional to the speed. The discharge head does not 
have to be throttled to regulate its capacity. The efficiency of the variable- 
speed direct-current motors used to drive triplex pumps is more nearly 
constant at variable load and speed than the efficiency of constant-speed 
motors is at the variable load used to drive centrifugal pumps. Small re- 
ciprocating engines have much better efficiencies at variable speeds than small 
turbines at variable loads. 

Comparing two types of boiler-feeding units, one a motor-driven cen- 
trifugal pump and the other a motor-driven triplex pump, taking into con- 
sideration the daily load curve of the plant and the efficiency curves of the 
two pumps, together with the efficiency curves of the two motors, it was 
found that the actual coal required by the triplex pump would be less than 
one-half that required by the centrifugal. A similar comparison covering 
steam driven units would show even greater difference in favor of the 
triplex pump. Against these advantages are, more space required, higher 
first cost, more complicated apparatus and more attendance. 

With stokers of the forced-draft type, states /. C. Hazvkins, the engine 
that drives the fan can be used to drive the triplex pump also. The feed 
pump is then operated at a speed in proportion to the amount of steam used 
and needs little other regulation. If automatic feed-water regulators are 
used a relief valve set at about 30 lb. in excess of the boiler pressure must 
be placed in the discharge line (probably by-passed back to the suction) to 
prevent overpressure. 

The triplex pump is simple, gives a nearly constant flow of water, and 
at all speeds has about equal efficiency, ranging from 70 to 85 per cent. The 
first cost of a pump and motor, however, is higher than that of a duplex 
pump. 

Methods of Driving Pumps 

\A OTORS are selected primarily because of plant conditions limiting the 
*-^'' use of steam from auxiliaries. Because of the difficulty of regulating 
its speed to meet the varying capacity demands the electric motor is not 
selected when steam power is permissible. If any of the power plant 
auxiliaries are steam-actuated, the boiler feed pump should be one. The 
alternating current motor must be run at constant speed, and the direct cur- 
rent machines equipped with complicated control devices if the speed is to 
be varied considerably. This speed variation is essential in feed pumps. 



310 A r X : L : A R T ^ 5 



For alternating current, the squirrel-cage induction motor is used. 
The starting current is high, hut a feed pump continues in operation 
for a considerable time, herce tre gre^T =:s.r::rr rirrtr.: lies not justify the 
use of a slip-ring motcr. 

On direct-cur -r": 5er-^::e i :::;:: i-l ::r ? usti T't series- 
wound is un5at:;:i:::r7 itri.Sf i: ..is i i :: f . :i .5 5. iir .y tiken 
o^ as when the Z-'-'-'-Z t; ::: rs 1; :r :: .: 1 : r ^: iii i 5 .::::::; Z'.\z shunt 
wound motor is Yaiiiaclr ::r r.iT 5tr its r. i:::.::.: :: ::5 : :r .:i: :-5: ee: 
characteristic. The co— ; . : 1- : . ii :.;::: ijtrii u: .ir.irr Asft.ei lii 
but not to E iir.reriu: ex:en:; it will slow down if overlziiei and thus 
furnish relief. 

Steam r. r::: e^ ire used principally with centrifugal pumps, as the high 

5;eef: ;_55i A :.. :. is ;inip are n:e: ~i::: i e: : :r. of cost and floor 
5;i:e. T.r les ire :.e:?ii^-!::!ica! £.: i: s:ee^r -A -600 r.pjn,>. The 
V i:tr r.:e.- :: Ae sreiri rrir.t :.:\i : e direct-acting purr, r are ::.:::- i 

Tr.e r.:r;Ae : = r :e rer.:'ated closely :: ~ee: - ir: A^ ^:— er le— ands. 
1:5 srei in be chs-.-irei eiAer manually or au:::.:i:icallv, by thrirr'irr the 



rr.-.ee. ir. 1 rrrri r.-irir siioiU'_ _e :r. :r.e s.'.i::, ;r 1 ..erii-ic coupuny suouiQ 

Stea::: erri-es r :: 1: s : r r ::i:: e fite: A '1 to 600 r.pjn,; 

this is tee .:\v Ar lire:: 1 t : :t: r^^ii : :::: s :::: are too large 

and costly when dn • e:: a: T: fits ^Ti:-ir: e ::r irr.:: : ral pumps is 

not desired, as the 'e'.: is A is 1 s ir:t :i riiAe 11 re t 1' expense. 

Steam engines are si s:e:: .7 :: :ir si it sitti r^^iA: ::: res, and 



Automatic Regulation of Pumps 



T 



limp consists of riie ireiiure regn- 
r : : - trol device at the boilers. 
en punq) discharge pressure by 
11; eing reduced so that with a 
sire 111 me feed- water lines is not 



boilers. 

In steam-acmaied pumps, uae pressiire regulator consists of a balanced 
valve, placed in the steam Ime to the pump, near the punq> valve chest. The 
balanced valve construction is used to render operation easier and prevent 
sticking. The cylinder of a piston on the throttle-valve stem conmonnicates 
with the feed-water hue so Uiat its pressure acts against the piston. When 
this pressure is increased, the stem is depressed, closing the v^e and throt- 
tling the steam to the prime mover so that the speed is reduced. A spring 
or loaded lever on the valve stem opposes the action of the piston, thus 
balancing the water force. The spring can be adjusted to maint aiii any 
desired pressure in the water lines. A diaphragm can be used instead of 
the piston and water cylinder for sio^lidty and to reduce the cost. 

The so-called constant excess-pressure regulator has the ;i~e ee e :? 
as a constant pressure regulating valve. The discharge v i:e- ;-is -f 
however, acts on one side of the piston or diaphragm and thr s e 11 

pressure on the other. The spring or loaded lever is adjusir 
difference between boiler and water pressure is maintained ccrs:ir.: iz 

ex:e5= pressure is just sufficient to force the feed water ir.:: the boiler. 



AUXILI ARIE S 



311 



This regulator is used with widely varying steam pressures to prevent 
the pump from discharging against too great a head when the steam pres- 
sure in the boilers is low. With a constant pressure governor, the water 
pressure must be sufficiently high to feed the boiler under maximum steam 
pressure. When the boiler pressure drops, the water pressure will be much 
greater than actually required, and the pump will be consuming more steam 
than necessary. 

Positive displacement power pumps are regulated either by varying the 
speed of the prime mover, or by a by-pass control, which opens the discharge 
from the pump to the suction, allowing the water to circulate through the 
pump. A check valve prevents the water in the discharge line from flowing 
back into the pump. 



("e-'/Po^^ 



^'-Gu/c/e Wheel 






,^ -Valve Sfew 
5 'A" Long 



Old Valve 
' Bonne-t 



^. WBolf Toip 
<%^^,^^;; , , 1/4 "Pipe Tap 

' It": VaWoles 

"r-l'/a" 

Close wifh 




To Service Wafer Pressure- 
Fig. 161, Details of a Motor-Driven Pump Regulator. 



SzcV\on A-A 



These machines are usually belted to a constant speed source of power, 
or are motor-driven ; the speed of the driver can be varied only when it is 
a direct-current or wound-rotor motor, and even then the control apparatus 
is likely to be unduly complicated. 

The essential elements of a constant excess-pressure governor for a 
wound rotor motor-driven feed pump are described by C. H. Sonntag as 
follows: The regulator, Fig. 161, works on the follow-up motion principle, 
such as is used on steam steering engines. The base casting is made from 




u 



o 









go, 
Co 

3 O 
!/l O 



a o 

::: a 

c a 

cQ a 
-Ho 

C C 
^> 

•2 ^ 
= 2 



Oh ^ 



^K 






AUXILIARIES 313 



an old motor rail. The diaphragm chamber and parts below it are from a 
V/i-'m. constant excess-pressure steam-pump governor. The motor used is 
of the wound-rotor type, and the three brush holders of the regulators, 
being in metallic contact with their supporting arm, short-circuit more or less 
of the resistance in the rotor circuit, according to their position on the face 
of the contact panel. The subdivisions of the rotor resistance are equal in 
the three phases, but corresponding sections of this resistance in the three 
phases are shunted successively instead of at the same time. This gives 
three times as many subdivisions of speed as there are contacts on the panel, 
and the result is smooth acceleration, with a speed for almost any rate of 
feed. 

The regulator does not open the primary circuit of the motor, nor stop 
it, but it will bring the motor down to a low speed. The pump is fitted with 
a spring-loaded relief valve set above the working pressure, which acts as a 
safety device when the discharge line is absolutely stopped. The panel is so 
connected to the resistance that the lowest position of the brushes shunts all 
the resistance. 

To start the pump and regulator, the valves leading to the upper and 
lower diaphragm surfaces are opened, also the one supplying service-water 
pressure to the follow-up. The drip valve should be open enough to let the 
plunger and the brush rigging down slowly when the follow-up valve is 
closed. The follow-up valve is then held open by raising the upper lever 
until the brushes are at the top of the panel and the primary switch is 
closed, when the motor will start slowly. The follow-up valve is released 
and the motor will accelerate up to the desired excess pressure. This is 
determined by the position of the 7-lb. weight on the lever arm, 15 lb. being 
about right for boiler feeding. 

When the plant is small and steaming is steady, the pumps are started 
and run until there is a good level of water in the gage glass. The pump is 
stopped when the level begins to rise too high, and started again when the 
glass begins to show that the water level is below normal. 

Centrifugal motor-driven pumps can be operated either with the by-pass 
or with the control described for the power pump. The capacity of centrifugal 
pumps drops off with an increase in head pressure ; consequently the pump 
speed tends to be regulated automatically, and pressures cannot become dan- 
gerous. This characteristic is not so pronounced that a centrifugal pump is 
independent of regulating devices. The control is usually of the by-pass type, 
consisting of a safety valve which under a predetermined pressure opens up 
and allows the discharge to flow back to the suction. This pressure is above 
normal, but is lower than the shut-off or zero capacity head of the pump. 

In steam-actuated pumps the control is simpler, since the speed can easily 
be changed by throttling the steam supply. With this method, power is not 
wasted by circulating water through the pump, and the pump is not constantly 
being stopped and started again. The supply is throttled by utilizing the rise 
and fall of water in the boilers, hot well, or open heater. 

Feed Water Regulators 

' I 'HE feed-regulator throttle-valve in the feed lines is controlled by the 
^ water level in the boiler steam-drum or in the hot well. The hot well level 
is used principally in marine service, and calls for operation on a closed 
circuit. The amount of water (in the form of liquid or steam) must be 
correct, therefore, in the entire system, — water lines, steam lines, and boiler. 

Regulators governed by the water level in the steam drum are of the 
continuous-feed type, in which the feed water flows at all times and the rate 



314 



AUXILIARIES 



of flow 15 regulated in accordance with the water level in the drum; or they 
are of the intermittent-feed type, and the water is fed or not fed, as the 
level falls below or exceeds a predetermined point in the steam drum. 

The continuous-feed regulator is designed to give even steaming and 
close regulation with slight danger of the water level dropping to a dan- 
gerous point. The water in the drum is not cooled off suddenly by the 
addition of large quantities of water, but feeding is continuous so that steam 
can be generated uniformh^ and most economically. 

One intermittent-feed regulator contains a vertical expansion pipe, the 
top of which is connected with the steam drum at the normal water level: 
the bottom of this pipe is connected with the steam drum below the normal 
water level. As the water level in the drmn falls, it also falls in the expansion 
pipe. Steam is then admitted to the pipe, thus increasing its temperature, 
since tlie water in the pipe is cooler than the steam. This increase in tem- 
perature expands the pipe and causes a motion that is transmitted to the feed- 
water valve-stem. The valve is thus opened and more water admitted. When 
water rises in the steam drum, the level also rises in the expansion pipe. 
The temperature of the expansion pipe is reduced, and the pipe contracts, 
closing the feed valve. Fig. 162 shows the design of this intermittent regu- 
lator. 



I ^Steam Connecfion 



tiorrr,al\ Wafer Level 




Fig. 162. Copes' Feed Water Regulator. 



In another t}-pe of intermittent regulator, a rise of water in the steam 
drum or water column above the normal is followed by the overflow of the 
water into a trap, thus opening it. Steam is then admitted to the pressure 
chamber of the feed valve, which is promptly closed. When the water 
level falls below the normal, the trap automatically closes. The pressure 
chamber of the feed valve exhausts into the hot well. 

Feed regulators of the continuous t>'pe take into account the rise and 
fall of water in the gage glass, due not only to the quantitj- in the drum, 
but also to the change in density of the water in the steam drum. When 
the boiler load is increased suddenly, steam is generated more rapidh- and 
the steam pressure drops. More steam bubbles will rise through the water 
in the drum, thus decreasing the density- of this water. The density in the 
gage glass remains unchanged. Hence the level in the gage glass rises more 
slowlv than does the water level in the drum, until the increased rate of 



AUXILI ARIE S 



315 



steam generation causes it to fall. The water level in the gage glass then 
falls, and the rate of feeding is increased in response, to maintain an even 
level in the glass. 

When the load falls off suddenly, the steam pressure is increased ; this 
is followed by a less rapid generation of steam and a reduction in the amount 
of steam bubbles rising through the water space. The density of the 
water in the drum is increased, while as before, the water level in the gage 
glass falls more slowly than does that of the level in the drum. When the 
evaporation is less rapid, the water level in both the steam drum and gage 
glass is ultimately raised; and the rate of feeding is reduced. Consequently 
rise and fall due to density changes and changes in level due to variation in 
the rate of evaporation, do not occur simultaneously. 

This lagging action is used in some continuous-feed regulators, which 
provide a strong feed during the decreasing load and lessen the feed rate 
in proportion to the evaporation rate when the load is increasing rapidly. 
Under decreasing load the furnace heat is thus stored, and is not wasted or 
discharged to the flues. When the load is increasing, the rate of feed is not 
increased greatly but Is kept as low as is consistent with safety. The furnace 
can then be used to generate steam instead of to heat large quantities of feed 
water. 




Fig. 163. Continuous Regulator of Float Type. 



In still another type. Fig. 163, a float normally rests upon the water in a 
chamber installed at the level of the water in the boiler drums. The rising 
and falling of the float is communicated to the throttle valve and thus regu- 
lates the feed continuously. The float can be partly filled with a volatile 
liquid, which expands because of the temperature changes in the float cham- 
ber. This expansion tends to equalize the external pressure on the float, due 
to the steam. The feed control valves used with the float are placed inside 
the regulating chamber, so that there are no outside stuffing boxes to be 
packed. 




o 



c 

M 
C 

'C 



•a 
t> 

a 
o. 



o 



as 

c 
c 

'o 

c 
O 



o 

c 

CO 



CO 

g 

CO 

02 

•d 
o 
o 

a 



A U X T T, T A R T R S 



317 



Location of Feed Pumps 

FOR cold water service, that is, water at 60 to 70 cleg., feed pumps give 
satisfaction with a suction lift as high as 15 feet. Generally, however, the 
suction lift of the feed pump is decreased by the temperature of the water. 
The atmospheric pressure which is equivalent to a head of 34 feet 
of water, forces the water into the pump. In practice, deductions must be 
made for the loss of head at the pipe entrance, pipe friction, valve friction, 
acceleration of water to its highest velocity, and pressure necessary to pre- 
vent vaporization of hot water. For example : 

Entrance loss, say - 2.0 feet 

Suction pipe friction 2 5 feet 

Acceleration, or velocity head 2.0 feet 

Pressure to prevent vaporization at 120°.... 3.9 feet 
Assumed lift 15.0 feet 



25.4 feet 
Available head for lifting suction valves 
and as a factor of safety for contin- 
gencies 8.6 feet 



Total 34.0 feet 

The velocity head of 2 ft. is a typical figure for a centrifugal pump, in 
which the water velocity through the eye of the impeller will be about 
12 ft. per second. 

Fig. 164 shows curves of suction lift or suction head for different water 
temperatures. The right-hand curve represents theoretical conditions as in 
the steam tables, or the pressure to prevent vaporization of the water. The 
curve in the middle represents the maximum suction lift or maximum suction 
head. For ordinary piping, the left-hand curve should be used. 

200 

Sl80 
«> 

L. 

1*160 

«) 
^140 

c 

a 
E 

f^lOO 

80 



60 





\ 




^--., 


•C^eo. 


















^<k 


N^c- 


^ 




?<x 


^^■^■^ 
















< 


l"^; 


^.xs 




^v.^ 


[^x, 
















%] 




?^ 




N 


\ 














"S^ 


h 


^'-% 

^X- 


'>. 




\ 
\ 
















X-o. 








\ 
\ 
\ 
















>^ 


^t 




\ 
\ 


















\ 




1 

1 





20 



10 -0 

Suction Pressure .Feet 



20 30 

Suction Lift, Feet 



4-0 



Fig. 164. Suction Lift or Suction Head at Different Temperatures. 

If the capacity is too high for a pump or suction pipe handling hot 
water the velocity head will be increased and the water handled will be 
vaporized. If the suction pressure is too low, or the lift is too high, the 
hot water will be vaporized. Vaporization causes knocking in the dis- 
charge lines and greatly reduces the capacity and efficiency of a direct-acting 
pump. The capacity will also be decreased with centrifugal pumps, since 
the water passages will be filled partly with vapor and partly with water. 

The effect of temperature on capacit}^ is shown by a test of a centrifugal 
boiler feed pump, due to John Howard. This was a 3-in. three-stage pump, 
designed for 150 gal. per min. against 195 lb. pressure, and was driven at 
3000 r.p.m. by a steam turbine. The water was measured by a flow meter, 
which was afterward calibrated and found correct. 



318 



AUXILIARIES 



The capacity test (see Fig. 165 > gave the results for a constaiit head and 
for constant speed. The first cur\-e was obtained by the use of a pump 

governor, and the second when the govern ;r is cut out, the capacity being 
varied bv throttlinsr the discharg^e. 



250. 



,3100 





^^v,^ 




^ - - 


"\.^ 


1 

• 1 




^^-. y^ 1 


230 


^Sre 


f- . ^^^ 


^vf^ 






. ->^ 






! ! J^^^^"^ 






^^.^-^ \ 




-"-^^ \ 


pr\/\ 


- \ i 


\ 


l = " 


\ 



c: 



30005 



in 
oj 

2900-^ 

-»- 
_c 

o 
2800.? 

■¥• 
C 



Z700 



o 

> 
« 



esoo 



40 



!60 



-z 



Fig. 165. 



Capacity Test for Hot Feed Water at Constant Speed 
and Constant Head. 



In making the :er.:pera:ure-capacir>- test t,Fig. 165) the temperature of 
the water in the open heater from which the pump took its suction was 
varied by controlling the amount of steam passing into it. The great varia- 
tion was undoubtedly- due to the extremely smaU head (only about 30 in. 
above the center-line) on the suction side of the pmnp. Because of this 
small head, the guarantee was only for 180 deg., but by speeding up the 
pump water at 190 deg. could be safely handled. 

The suction lift should be kept low or the suction pressure high in ac- 
cordance with Fig. 164. The suction pipe should be as direct as possible 
with no imnecessary elbows or valves. The suction piping should be of 
generous size; a velocity- of 2 ft per second should not be exceeded for hot 
water. 

Suction pipes should be accessible for inspection and arranged so that 
valve spindles can be repacked easih-. Particular care should be taken to 
avoid leaks in the suction pipe. These do not show directly on the dis- 
charge side, although they are sometimes indicated by a ""jump"' of the pump 
at the start of everj- stroke. 

With long lines or deep lifts, the line and ptunp can be kept "primed" 
by a check or foot valve at the bottom. With long suction lines, more par- 
ticularly with single CA'linder pumps, an air vessel should be fitted on the 
line, to prevent knocking. 



AUXILI ARTE S 



319 



Injectors as Boiler Feeders 

INJECTORS are made in many forms, but Fig. 166 shows the typical ar- 
rangement and illustrates the method of operation. Steam is admitted 
through the valve M, by turning the handle K, and enters the expanding 
nozzles where the pressure is reduced and the velocity greatly increased. The 
steam jet is then guided to the contracting nozzle or lifting tube V. In 
passing from the first to the second nozzle it carries along the air in the 
chamber and creates a vacuum. The water to be pumped rises in the suc- 
tion pipe and fills the chamber. The steam and water thus enter the lifting 
tube, passing to the mixing nozzle C, and the steam is condensed. When 
the water and steam have reached the delivery nozzle D the steam has been 
condensed and the water is traveling at a high velocity imparted to it by 
the steam. The delivery nozzle is increased in cross-sectional area, reduc- 
ing the velocity and hence increasing the pressure of the water. Conse- 
quently its head is sufficient to overcome the resistance of the feed valve, 
and the water enters the boiler. The steam has thus imparted kinetic energy 
to the water ; this energy is converted from velocity to pressure in the de- 
livery nozzle. The water is heated through the condensation of the steam. 

The action of the injector depends not only upon the impact of the jet 
of steam, but also upon its efficient and complete condensation, which must 
occur during its passage through the combining tube. At 180 lb. boiler pres- 
sure the water must attain a terminal velocity of 163 ft. per sec. to balance the 
pressure, and something more to lift the check valve and enter the boiler. 
If the total length of the converging combining tube is 7^ in., the interval 
of time during which the steam can be condensed is only 0.008 of a second 
and the acceleration is 4 miles per second per second. 

Anything that tends to diminish rapid condensation operates against 
mechanical efficiency. An increase in the temperature of the water supply, 
moisture or superheat in the steam ; all tend to reduce the proper ratio be- 
tween the weight of the water delivered into the boiler and that of the 
motive steam. The steam must undergo instant and complete condensation, 
and its velocity must reach a maximum at the instant of impact with the 
water. 

-K 




i/'5team 



Fijg. 166. A Boiler Feed Injector. 




Lytton Building, Chicago, 111., containing 1500 H. P. of Heine Standard Boilers. 



A U X I L I A R I 1^: S 



321 



Experiments with saturated steam prove that the flow is in accord with 
the well-known formula based upon adiabatic expansion. The velocity of 
superheated steam is slightly higher as it follows the law of a perfect gas 
until condensation due to expansion begins; the velocity of the combined 
jet would consequently be increased, but this advantage is overbalanced by 
the shorter interval of contact and condensation, during which the additional 
heat in the steam must be abstracted. Consequently the mechanical efficiency 
is lowered. To obtain good results with superheated steam, the injector tubes 
and nozzles must be specially designed. 

The practical effect of superheated steam upon the action of an injector 
is to reduce the maximum capacity, increase the minimum capacity, and to 
lower the limiting temperature of the water supply with which the injector 
can operate. Further, with high pressure and superheat, an inefficiently de- 
signed instrument is inoperative. It is therefore advantageous and usually 
practicable to supply the injector with saturated steam through a special pipe. 

The steam pressure range over which an injector will work depends upon 
the distance between the steam nozzle and the lifting tube. With a fixed dis- 
tance between these two points the injector will operate only with a pressure 
range of about 75 pounds. If the injector is designed for 175 lb. maximum 
pressure the minimum steam pressure under which it will operate will be 
100 pounds. After the maximum and minimum pressures are passed the 
ratio of steam velocity to quantity of water for complete condensation of 
the steam is not correct. The injector can be operated only by throttling 
or opening its suction line, or by varying the distance between the steam 
and lifting nozzles. 

Commercial devices are supplied to render the injector operative over 
a wider steam pressure range. In one type a half turn of the valve handle 
allows the nozzle to remain in one position so that the pressure range is 
90 or 100 lb. maximum. A full turn of the handle changes the position of 
the nozzle, giving a higher range of steam pressures, 100 or 175 pounds. 
The action of this type is indicated in Table 39. 



Table 39. 


Steam Pressures at Lifting Nozzles of Injectors. 


Lift, 




Feed Water at 72 Deg. 


Feed Water at 100 Deg. 




Start 


Works up to 


Start 


1 

j Works Up to 

1 


Not lifting 


1 

20 160 
25 150 
30 130 


25 

26 
33 


125 


2 

8 


i 120 
i 100 


14 

20 


42 
80 


110 

85 


55 


80 







Another injector has a double set of nozzles; the first lifts the water and 
delivers it to the second, which acts as a forcing nozzle to deliver the water 
to the boiler. The capacity of this type can be changed by varying the 
amount of steam admitted to the lifting nozzle. The quantity of water varies 
directly with the steam pressure at the lifting nozzle ; this reduction in 
water is desired for the proper functioning of the forcing nozzle. Any 
change in steam pressure or in quantity of water to condense the steam thus 
affects both nozzles, so that pressure changes require no hand adjustment. 
This type has operating characteristics as indicated in Table 40. 



322 



AUXILIARIES 



Table 40. Steam Pressures at Lifting Nozzles of Injector. 



Lift, 
Feet 



Feed Water Temperature 



72 Deg. 



100 Deg. 



120 Deg. 



140 Deg. 



Start 



Up to 



Start 



Up to I Start j Up to 



Start 



Up to 



Not lifting 


25 
25 
35 


350 
300 
270 


25 
30 
40 


265 
265 
235 


35 
35 
45 


230 
230 
205 


35 


140 


2 




8 


45 


110 


14 

20 


45 
65 


240 
185 


50 
70 


210 
155 


55 
65 


140 
120 











Another type, commonly called an inspirator, Fig. 167, has two nozzles, 
but the steam pressure cannot be adjusted at the lifting nozzle. The lifting 
and forcing nozzles receive steam from separate openings, so that the steam 
pressures can be adjusted separately through valves in the steam lines. 



^Si-eam 



Wafer- 




Fig. 167. 



An Inspirator Type Injector. 



In all injectors a check valve is placed in the mixing chamber, with 
openings into the mixing nozzle, so that in starting, before water is drawn 
into the mixing tube to condense the steam, the mixture of steam and air 
can escape to the atmosphere. When the steam is condensed a partial vacuum 
is formed in this chamber and the check valve automatically closes, opening 
only when condensation fails. 



AUXTLTARTES 323 

The thermal efficiency of an injector, considered as a pump only, is about 
2 per cent. As a combined pump and feed-water heater the thermal efficiency 
is nearly 100 per cent, the only heat of the steam not returned to the boiler 
being a small percentage lost by radiation. If the exhaust steam available for 
feed-water heating is not sufficient to heat the water above its limit possible 
with the injector, the latter is a good feeding apparatus. On the other hand 
the injector is not so economical if it interferes with the economic use of 
exhaust steam in the plant. It is rarely installed as the main feed unit, 
unless in small plants where a feed pump might not receive attention. The 
injector, however, is so reliable, compact and inexpensive that it almost always 
is placed in the boiler room as an auxiliary feed device, to be used should 
the main feed pumps become inoperative. 

Many plants operate at high over-all economy during the heating season 
when all the exhaust steam is utilized, but decrease their economy when 
the exhaust is wasted to the atmosphere. Extra exhaust, winter or summer, 
can be used to feed the boilers by means of an exhaust steam injector. The 
heat taken from the boiler in the form of steam is nearly all returned at 
once by the live-steam injector, but the exhaust-steam injector returns heat 
to the boiler that is about to escape through the engine exhaust pipe. The 
water so condensed is free from scale-forming matter, but all oil should be 
removed from the exhaust steam. Restarting an exhaust-steam injector is 
not difficult when the water flows to it under pressure or live steam is 
available. 

Air entering the injector will always cause a "break," so that unusual 
care should be taken to avoid leaks in the suction pipe. With some waters 
trouble is caused by scale in the lifting, mixing and discharge nozzles ; this 
is probably due to evaporation to dryness of water remaining after a stop. 

Economy of Feed Water Heating 

T^HE principal function of a feed water heater is to utilize the heat from 
-■- exhaust steam or flue gases, which would otherwise be wasted. The per 
cent of saving effected by heating the feed water may be expressed by the 
following formula : 

Per cent saving = 100 ^ ^ C28^ 

H—{t,—Z2) ^ ■' 

where h = the temperature of water entering the heater, t^ = the tempera- 
ture of water leaving the heater and H = the total heat above 32 degrees 
per pound of steam at the boiler pressure. 

Feed water heating results in the further advantages : first, of increasing 
the steaming capacity of the boiler by eliminating the heat required for 
heating the feed water ; second, by its action as a purifier certain scale- 
forming ingredients in the feed water are removed; and third, by feed- 
ing water into the boiler drum at or near the steam temperature the tendency 
of setting up temperature strains in the boiler metal is eliminated. 

Classification of Feed Water Heaters 

T-J EATERS may be classified into three main groups, viz: closed heaters, 
■'■ -'■ open heaters and economizers. Open or cloged heaters may utilize ex- 
haust or live steam, while economizers utilize the waste heat in the exit flue 
gases. The selection of one or more of these types of heaters will depend 
largely upon conditions at the particular plant in question. 

Open heaters may be of three different types. In the one type, generally 
known as the live steam purifier, live steam is used to heat the feed water 
up to a temperature of approximately 300 degrees in order to precipitate out 





o 





a 

■4-1 

w 



3 

o 
in 

a 

C 

+j 
o 



CO 



O 
O 

o 



OS 
o 

'2 

H 



AUXILIARIES 



325 



such scale-forming elements as the sulphates of lime and magnesia. The use 
of the live steam purifier should be confined to those plants where the feed 
water contains sulphates. 

A second type of open heater is designed for the use of exhaust steam 
at atmospheric pressure or less, while the third type is designed for the use 
of exhaust steam at back pressure up to 10 or 20 lbs., depending upon the 
back pressures on the auxiliary engines and pumps. 

In the open heater, Fig. 168, steam enters the opening of the shell on 
one side, pear the top, and passes through an oil separator into the mixing 
chamber. The cold feed water enters at the top of the shell, and passes 
over and through a set of perforated trays, where it is broken into fine 




Fig. 168. Cochrane Metering Open Feed Water Heater. 



particles, to insure thorough and intimate contact with the steam. The mix- 
ing of steam and water condenses the steam and the mixture, or hot water, 
falls to the bottom of the shell through a bed of filtering material. A float 
controls the amount of water entering the heater so that a constant water 
level is maintained at the bottom. An overflow provides against the water 
level rising too high in the shell and backing up into the exhaust steam lines, 
should the float control become inoperative. 

Since the heat given up by the steam, plus the losses due to radiation, must 
equal that gained by the water, the amount of steam to raise a given amount 
of water to a desired temperature, is easily calculated, as is also the resulting 



326 AUXILIARIES 

feed-water temperature, when the amounts of steam and water are given. The 
radiation losses can be made negligible with proper insulation, so this factor 
is eliminated in the formula : 

(f,— fO JJ'= (H — 32 — t,) S 

— = — ^'~^' (29) 

JV H-i-32 — t, ^ 

tz =: Temperature of water to boilers (hot) 

fi = Temperature of water to heater (cold) 
H = Total heat of steam at back pressure conditions. B.t.u. 

S = Weight of steam, pounds 
W z= Weight of water, pounds. 

The heat of the liquid at the two temperatures should be used for exact 
calculations, but the foregoing is sufficiently accurate for commercial pur- 
poses. 

In selecting an open heater, the following features should be considered : 

1. Skc. The heater must have sufficient steam space and tray area. 

2. Oil Separator. This is necessary if exhaust steam contains oil, as 
when reciprocating-engines or pumps exhaust into the heater. Oil 
must be efficiently separated and drained off. 

3. Filter Bed. This is frequently omitted. 

4. Hot Well, or space at bottom must be ample so as to act as a settling 
basin and reservoir for the feed pump. Vapor vent should be pro- 
vided for escape of air and vapor. ( Hot well can also be used as a 
purifier space.) 

5. Re^nlaiing J^alz'e Is necessary- to maintain proper water level in the 
shell. 

The design should also be considered in the light of its applicability 
to plant requirements. 

That part of the heat so used which is not converted into work is re- 
turned to the boiler instead of being rejected to the condenser circulating 
water, giving the maximum thermal efficiency. 

In one heater an indicating and recording mechanism is supplied to 
measure the feed water, so that the quantity- can be checked closely and the 
heat balance and performance easily calculated. These devices are valua- 
ble in order to maintain a running check on performance. 

When the exhaust steam pressure is above atmosphere, exhaust valves are 
used on the heater or exliaust steam lines. These allow the steam to be ex- 
hausted to the atmosphere or to the low pressure end of the main turbine. 
In one valve a nest of spring-loaded relief valves performs this function. These 
valves have individual dash pots. The action with them is smoother and less 
likely to stick than with one large valve. The tension of the valve springs 
can be regulated by a handwheel from outside the valve. The high back 
pressure that may be required in the morning to run the heating system can 
be decreased in the afternoon when the buildings have been warmed. 

A thermostat can be attached to a heater to control the drives of auxili- 
aries. These can be arranged for double drive, with motor on one side and 
turbine on the other. When too much steam is exhausted to the heater the 
pressure in the exhaust lines is raised, and the temperature is increased. The 
thermostat then operates to throttle the turbine, and more of the load is 
taken by the motor. Thus less exhaust steam is supplied, and the excess of 
steam is reduced in proportion. When the supply of steam in the heater is 
insufficient, the pressure in the exhaust line drops, the temperature is re- 
duced and the thermostat permits more steam to flow to the turbine. The 
turbine then picks up the load and furnishes more steam to the heater. 



AUXILIARIES 



327 



Relief valves can be used to bleed steam from one of the low pres- 
sure stages of the main turbine and lead it to the heater during periods 
of low pressure in the exhaust line. A high feed-water temperature is thus 
maintained. 

Closed feed water heaters may be grouped into two classes, steam tube 
and water tube. Those in which the steam passes through tubes and the 
water is contained in the heater shell are known as steam tube types, while 
those in which the water flows through the tubes and the steam is con- 
tained in the heater shell are classified as water tube types. Steam tube and 
water tube heaters may operate on the parallel current or counterflow 
principle, and they may be designed so that the steam or water makes one 
pass through the heater (single flow), or so that the steam and water may 
make several passes (multi-flow). 




Expansion End 

wi+h both 
Heads Removed 



£:?(haust\Ou+lei \ 
A \ 




Feed Inlef End 
wi+h Head Removed 

^ Fetal Inkf 



Section 
Thru A-B 

Fig. 169. Closed Feed-Water Heater. 

Fig. 169 illustrates a typical closed water tube feed-water heater of the 
multi-flow type. Water is circulated in six passes to insure maximum heat 
transfer from steam to water. The number of passes varies, but two is the 
usual practice. Tubes are secured to tube sheets by screwing, welding or ex- 
panding. In some designs each tube is packed with ferrule glands, to simplify 
replacements. 

The floating head construction provides for expansion and contraction of 
the tubes under varying temperatures. This feature is important when 
straight tubes are secured rigidly at each end to the tube sheet. 

Most closed heaters are arranged so that they can be installed either 
vertically or horizontally, as best suits the space and piping. 

The Patterson-Berryman closed feed-water heater, illustrated in Fig. 
170, is of the water tube type. The water makes a double pass through 
inverted U-tubes, while the steam passes through the body of the heater. A 
chamber at the bottom, provided with a blow-off connection, serves as a 
receptacle for the collection of scale, sediment, etc. 

In one heater, Fig. 171, coiled water tubes are connected to the top and 
bottom water headers with special leakproof unions. The coils allow for ex- 
pansion and contraction of the tubes and present maximum heatmg surface 
This type is of the one-pass design, water entering at the bottom header and 
leaving from the top. Tubes are examined or repaired through a door in 
the front of the shell. 



AUXILIARIES 



329 




Fig. 170. U-Tube Feedwater Heater. 

Open or Closed Heaters 

"T^HE general construction of the power plant usually determines the type of 
■'- heater. In marine service, for instance, because of space limitations and 
the rolling of the ship, closed heaters are usually installed. Open heaters 
adapted to this service are in general use, how^ever, by the English mercantile 
marine. In ice plants the closed heater might be preferable, since the con- 
densed steam would be available for ice-making ; on the other hand, much 
better ice is made with the open heater, because it acts as a reboiler, driving 
off the air and other gases, which purge off through the vent. With closed 
heaters this air passes through the heater into the boiler an-d engine. A 
greater amount of boiling is then required in the reboiler, with greater waste 
of steam. Vacuum reboilers are sometimes found inadequate, and the 
capacity must be increased by the use of atmospheric reboilers. 



330 



AUXILIARIES 




---.-- / 




Fig. 1,1. Mill ti- tubular Feedwater Heater. 



The two types are compared in the following tabulation: 



Open Heater 



Closed Heater 



Lfficiency 



With sufficient exhaust steam for 
heating, the feed water can reach 
the same temperature as the enter- 
ing steam. 

Scale and oil do not affect the 
heat transmission. 



The maximimi temperature of the 
feed water will always be several 
degrees lower than the temperature 
of the steam. 

If the scale or oil are deposited 
upon the tubes, heat transmission 
is lowered. 



Pressures 

It is not ordinarily subjected to The water pressure is slightly 

much more than the atmospheric greater than that in the boiler, when 

pressure. the heater is placed on the pressure 

Can be made, however, for back side of the feed pump, as is ens- 
pressures of 15 lb. or more. tomar\-. 



A U X T L T \ R T K S 331 



Safety 

If the heater is to be used with It will safely withstand any ordi- 

a back pressure, a good valve, pre- nary pressure. However, any shut- 

ferabl}^ with more than one disk. off valve in the feed line should be 

should be fitted. Otherwise, the placed between the feed pump and 

back pressure valve might stick and the heater, with a check valve be- 

blow up the heater. tween the heater and the boiler. 

Purification 

Since the exhaust steam and feed The oil does not come in con- 

water mingle, provision must be tact with the feed water. 

made to remove the oil from the Scale is removed only with diffi- 

steam. culty. 

Scale and other impurities pre- 
cipitated in the heater are easily 
removed and do no harm. 

Corrosion 

The open heater prevents cor- With the closed heater the oxy- 

rosion by driving out oxygen orig- gen is not discharged and corrosion 

inally dissolved in the water. of piping and boilers occurs. 

Location 
Must always be placed higher May be placed anywhere on the 

than the pump on the suction side. pressure side of the pump. 

The greater the vertical distance 
between the pump and heater, the 
better. 

Feed Pumps 
With supply under suction two Only one cold-water feed pump 

pumps are necessary and one must is necessary. 

handle hot water. 

Adaptahility 
Particularly adaptable for heat- Adapted to use in small space, 

ing systems and wherever the re- and when condensate of exhaust 

turns are piped directly to the steam can be used in process work, 

heater. 

Economizers 

THE economizer is a closed feed-water heater utilizing the hot waste gases 
of combustion. As a piece of apparatus for the promotion of boiler 
room economy, the economizer is rapidly gaining favor, due to increasing 
prices of fuel, and to the large stack losses inherent with the present prac- 
tice of forcing boilers to high ratings. 

Two types of economizer may be met in practice, one in which the 
economizer is an integral part of the boiler and the other in which it is an 
independent unit. When an economizer forms an integral of a boiler its 
design is generally such that steel tubes, headers and drums have to be 
used. Inasmuch as there is extreme liability for corrosion due to the con- 
densation of moisture or sweating of the outside of economizer tubes, cast 
iron should be used rather than steel, due to its lesser tendency to fail 
by corrosion, unless there is some special method taken to prevent the cor- 
rosion of the steel. 

Fig. 172 illustrates one widely used type of independent economizer. It 
consists of vertical cast iron tubes, which are arranged in sections in the flue 
leading from boiler uptake to stack. When in position the sections are com- 
posed of bottom and top headers into which the tubes are pressed, a metal-to- 
metal joint being formed. The top and bottom headers of the sections are 
connected to branch pipes, one extending lengthwise at the top of the 
economizer and the other extending lengthwise at the l)ottom. Both top and 




Hotel St. Regis, New York City, operating 1450 H. P. 
of Heine Standard Boilers. 



AUXILIARIES 



333 




!*<Ka^>w r 



Wtt«tOttU«( 




Fig. 172. Green Fuel Economizer. 

bottom branch pipes are located accessibly outside of the economizer setting 
or casing. The feed water enters the economizer through the lower branch 
pipe nearest the gas outlet of the economizer and leaves through the upper 
branch pipe nearest the point where the flue gases enter the economizer from 
the boiler. 

Either mechanical soot blowers or mechanically operated scrapers may 
be used for cleaning the external tube surfaces. If scrapers are used, their 
operating mechanism is generally placed on the top of the economizer. The 
motive power for scraper operation may be supplied from some convenient 
line shaft or by individual motor or engine. 

Blow off valves and safety valves must be provided with economizers. 
For flexibility and continuity of boiler operation it is desirable to have 
a by-pass flue from boiler uptake directly to the stack. Inasmuch as gas 
explosions sometimes occur within economizer settings, it is desirable to 
provide quick opening explosion doors therein. 



Economizer Performance 

THE stack gases in a boiler indicate the amount of heat available for feed- 
water heating. Table 41 gives roughly the heat content of the gases of 
combustion in the flues and uptakes. 

If the fuel has a heat value of 10,000 B.t.u. per pound, the stack gases 
are at 500 deg., and the stoker is of the overfeed type, then Table 41 shows 
that the heat in the stack gases will be about 18.2 per cent, or 1820 B.t.u., 
for every pound of fuel consumed in the furnace. The difference between 
the heat in the gases entering and leaving the economizer represents the 
saving. In the example just mentioned, if the gases leave at 350 deg., they 
contain 12 per cent of the heat in the fuel ; the economizer then saves 6.2 
per cent. 

The economizer is most useful, therefore, when the heat of the stack 
gases is greatest in proportion to the heat of the fuel or when the losses 
would ordinarily be the greatest ; as with an overloaded boiler, hand-fired or 
having an overfeed stoker and draft. The overload on the boiler will be 
indicated by high stack temperature. As is shown by Table 41 with normal 
load and efficient firing, the stack losses may not be sufficient to warrant 
the expense of an economizer. The stack gases will not heat the feed water 
appreciably, unless the economizer is large and costly. 



334 A U X T L T A R T E S 

Table 41. Heat of Fuel in Percent Present in Flue Gases. 

Flue-Gas Underfeed Stoker. Oveneed or Narural Hand Firing, 

Temperarure, Degrees Forced Draft Draft Stoker Natural Draft 



Air per lb. of combust- ^ ..^ ' .^, 

ible, lb i ^^ I ^ 



30 



300 .... .... 12.4 

350 .... 12.0 14.9 

400 .... ' 14.0 17.4 



450 , 12.2 16.1 i 20.0 

500 13. S ' 18.2 ' 22.6 



550 


15.4 


20.3 


25.2 


600 17 


22.4 

1 24.4 

26.5 


27.8 


650 

700 


18.5 1 
20.1 


30.4 


750 

800 


21.7 

23.2 







The method of calculating economizer performance is given by A. B. 
Clark as follows : Assume that the economizer is to be so proportioned 
that the combined efficiency of both boiler and economizer will be 80 per 
cent the coal containing 10.000 B.t.u. per pound. The steam has a pressure 
of 250 lb. gage, and 250 deg, of superheat, the feed water entering the 
economizer at 100 deg. The heat contained will then be 1340 B.t.u. per 
pound of steam. The feed water contains 68 B.t.u., so that the heat 
given up by boiler and economizer is 1272 B.t.u. per pound of steam. As 
the efficiency is 80 per cent, 8000 B.t.u, of the 10.000 B.t.u. in each 
pound of coal is used, and the evaporation is 8000 -^ 1272, or 6.Z lb. of water 
per po'ind of coal. 

Allowing for excess air and infiltration of air, about \22S lb. of flue 
gases will be produced per pound of coal burned. If the radiation loss is 
neglected, the heat given up by the flue gases must equal the heat absorbed 
by the water ; that is. the product of the specific heat, weight and drop of 
temperature of the flue gases must equal the product of the specific heat, 
weight and rise of temperature of the water. 

Let tg represent the drop of temperature of the flue gases and tw repre- 
sent the rise of temperature of the water. Then 

0.24 X 1225 X f^ = 1 X 6.3 X ^«' 

ig _ IX 6.3 ^ 14 
tii- ~ 024 X 1225 

This means that for even.- degree of temperature increase of the 62 lb. 
of water, the 1225 lb, of flue gases will drop 2.14 deg. in temperature. 

The water passing through the economizer is taken as 100.000 lb. per 
hour, which the boiler, it is assumed, can evaporate. The temperature of 
the gases leaving the boiler is taken as 600 degrees. 

The average temperature difference between the water and gases in the 
case assumed above is 4S4.3 degrees. Tests on economizers show that 
the rate of heat transfer from gas to water is about 5.5 B.t.u. per square 
foot of surface per hour per degree temperature ditterence between the 
gases and the water, when the economizer is proportioned for a gas flow of 
B.OOO lb. per hour per square foot of area. It will be 4 B.t.u. per square 
foot if the flow is reduced to 3,000 lb. per hour and in proportion between 
these two points. 

The water usualh- flows through all of the sections in parallel. With long, 
narrow economizers and where the gases have a large drop in temperature 
the economizer is .sometimes subdivided into groups, through which the 
water is passed in series, progressing in a direction counter to that of the 



AUXILIARIES 



335 



gases, thus obtaining- a greater total transmission of heat according to the 
counter-flow principle. The individual sections can also be connected in 
series, but this complicates cleaning and blowing down. 

The transmission coefficient varies with the mean gas temperature as 
shown in Fig. 173, due to Geo. II. Gibson. The rate of heat recovery by the 

6.0 



5.0 



4.0 



cci w 

c cy 



O 61 3.0 



.!2 i- 

^ r\ 



2.0 















/ 






































/ 








y 




























^^' 


y 






y 


y 






,.^ 


^ 






















7\ 


r 


\ 


p 


X 


|00° 


f^ 


^ 
























J 


/ 




y 


^ 


^ 


j> 




3001 


h , 























/ 


/ 


/ 


y 


x- 




H 


























/ 


f 


/. 


/ 


y 


^' 






























/ 


/ 


/. 


y 
































/ 


// 


/> 


/ 


































/ 


y/ 


/ 





















































































































3G0 



1?0 1080 1440 1800 2160 2520 

Gas Flow, Lb. per. Hr. per Ft of Pipe in Sec+ion 



Z880 



3240 



3600 



Fig. 173. Variation of Coefficient of Transmission with 
Mean Gas Temperatures. 



1800 

1700 

IGOO 

1500 

cl400 

L 1300 

^1200 



o-llUU 
to 

biooo 

S'900 

CO nnn 



Z 700 

8 wo 

o 

^ 500 

-t- 

^ 400 

300 
200 
100 











1 — 
































f"™" 


Ti, 








































y 


y^ 


A 


\ 

\ 






































/ 


y 


/ 




y 




































.A 


^fy 


/ 


^ 


^ 
























•4 










j^/ 


/A 

y 




y 


























.^^ 










\^. 


Z 


A 


V 


t« 


























^ 


f 








4 


/y 


4^^. 


[</ 


t*!' ■■ 


























/ 




,> 




? 


^0^^'f' 




























.f 


t 






y 


:^ 


'y 




^(i-^ 






























L 


A 


•i' 


A 


<^ 


4 


,r 






























4 


K 


/ 


** 


A 


'^ 


/^ 


yu 
































^y 


/ 




^ 


^y 


/^ 


































4 


V 




^ 


y 




































^ 


f/ 


r 


^ 


y 




































f// 


> 


^ 


/^ 




































i 




y^ 


















































































A 















































I Z 3 4 5 



6 7 8 9 10 II 12 13 14 15 ' 16 17 18 19 20 l\ 11 Th 
Water. Flow, Lb. per 5q. Ft. per Hour 



Fig. 174. Variation of Rate of Heat Recovery by the Economizer. 




1400 H. P. of Heine Standard Boilers equipped with Murphy Stokers, 
in the Fifth Avenue Building, New York City. 



AUXILIARIES 



337 



economizer increases directly as the load on the boiler to which it is con- 
nected. This is shown by Fig. 174, also due to Geo. H. Gibson. The heat 
recovery while the load is increasing appears to be somewhat less than while 
it is decreasing, owing to the fact that the rate of heat recovery can be 
determined only by measuring the temperature of the water as it leaves the 
economizer. 

Using the higher value for calculation, the heat transfer per square 
foot per hour is 5.5 X 484.3, or 2663 B.t.u. Therefore the surface required 
to raise 100,000 lb. of water through 10 deg. is 100,000 X 10 -i- 2663 = 376 
sq, ft. The next step is to assume new values for gas and water temper- 
atures and calculate the surface required. 



Table 42. General Dimensions of Economizers. 



12 
12 



No. of 
Tubes 


Length of 
Tubes, 
Feet 


Weight of 

Section Full 

of Water, 

Pounds 


External 

Heating 

Surface, 

Square Feet 

per Section 


Number of 

Sections 

in 

Economizer 


Length Over 
Economizer 


Wide 


Ft.— In. 


4 
4 
4 


9 ' 1,636 

10 1,756 

11 1 877 


51.0 
55.8 
60.7 


i 

4 2—5 

8 4—10 

12 7— 3 


4 1 12 1 2,005 65.4 ! 16 
6 19! 2,388 | 76.5 i 20 
6 i 10 ' 2,570 1 83.8 j 24 


7— 8 
12— 1 
14— 6 



6 


11 


2,751 


91.0 


28 


16—11 


6 


12 


2,942 


98.3 


32 


19— 4 


8 


9 


3,096 


102.0 


36 


22—113/^ 


8 


10 


3,337 


111.7 


40 


25— 43^ 


8 


11 


3,578 


121.4 


44 


27— 93^ 


8 


12 


3,885 


1 131.0 


48 


31— 5 


10 


9 


3,760 


127.5 


52 


33—10 


10 


10 


4,061 


: 139 . 6 


56 


36— 3 


10 


11 


4,363 


1 151.7 


60 


38— 8 


10 


12 


4,684 


; 163.8 


64 


42— 33^ 


12 


9 


4,380 


153.9 


68 


44— sy2 


12 


10 


4,742 


167.5 


72 


47- 13/2 



49— 63^ 
53— 2 



As the temperatures of the water and gas approach, the surface must 
be increased for a given rise of the water temperature. The ashpit loss will 
be about 3 per cent and the unaccounted-for losses and radiation are about 
3.5 per cent. As the efficiency of boiler and economizer is 80 per cent, the 
flue-gas loss will be 13.5 per cent, or 1350 B.t.u. per pound of coal. 

Flue gases from the coal will contain about 0.5 lb. of water in the form 
of superheated steam ; therefore, as the total weight of the gases is 12.25 lb. 
per pound of coal, the gases will weigh 11.75 lb. and the water vapor 
0.50 pound. 

Assuming that the air entering the boiler is at a temperature of 70 deg. 
the temperature of the escaping gases can be found from the equation, 
11.75X0.24 (^ — 70) -f 0.5x0.48(f — 212) 4-0.5 X 970.4 
H- 0.5 (212 — 70) = 1350 
t = 340 deg. 
If the final gas temperature is 340 deg. the surface required is 8,000 
square feet. The feed-water temperature will be 220 deg., a rise of 120 




Cook County Court House, Chicago 111. containing 1830 H. P. 
of Heine Standard Boilers. 



AUXILIARIES 339 



deg. from the assumed initial temperature. The return in heat units per 
pound of coal is fired is 6.3 X 120 = 756 B.t.u., or a return of 7.56 per cent 
on a heat value of 10,000 B.t.u. 

Having determined the surface area of the economizer, the space require- 
ments can be checked with fair accuracy from Table 42, which gives the 
dimensions of the economizer made by a prominent manufacturer. Tliis 
table will apply as a general guide in determining the room required. 

Air Heaters 

HEATING the air supply to furnaces by abstracting heat from the exit 
gases is just as logical a method of saving fuel as is heating the feed 
water in the same way. The saving effected can be directly measured by 
the drop in temperature of the flue gases in passing through the air heater, 
or by the rise in temperature of the air, when the weights of air and gas per 
pound of fuel are known. 

Usually the gases are passed through vertical pipes of about 3-in. bore, 
around which the air flows horizontally. In a system recently described 
by /. Van Brunt, the heater consists of a nest of semi-circular plates ar- 
ranged in pairs so that the air flows in a path curved circumferentially from 
inlet to outlet, while the gases flow between the plates in straight chordal 
paths. This design makes a very compact and convenient arrangement. 

The rate of heat transmission varies with the cleanliness of the surface, 
with the gas and air velocities, and with the difference in temperature be- 
tween the gas and the air. Consequently, the areas of the passages and of 
the heating surface are directly related. 

In Table 43 the symbols have the following meanings : 
IV =: Weight of air or gas, pounds per hour. 
A ■= Area of passages, square feet. 

R = B.t.u. transmitted from flue gas to air per square foot of 

surface per hour per degree difference between average 

temperatures of gas and air. 

Table 43 can be entered with IV/A, and the value of R found. The 

heat (in B.t.u.) to be transmitted per hour divided by R times the average 

temperature difference between the gas and air is the heating surface required. 

Table 43. Heat Transmitted Between Flue Gases and Air. 



W 

A 



Values of R at Temperature Differences 



100 I 200 I 300 



1,000 
2,000. 

3,000, 
4,000 



1.6 1.7 i 1.8 

1.9 2.3 ! 2.7 

2.2 2.9 t 3.7 

2.5 I 3.5 ; 4.6 



This table has been prepared on the assumption that the values of JV/A 
for gas and air will not vary more than 10 to 15 per cent. The area through 
the tubes is commonly from 30 to 50 per cent greater than that of the equiva- 
lent breeching. The air passages can be proportioned in the same manner 
as directed in Chapter 6 on CHIMNEYS, allowing for the temperature of air 
desired, and making the area between the tubes the mean of the hot and cold 
air ducts. The loss of draft through a well-designed heater will be about 0.1 
in. of water column. The loss of air pressure will be from 0.1 to 0.2 in.; 
and to this must be added the resistance of the air ducts, making allowance 
for bends that cannot be avoided. 




o 
PQ 



C 
CB 

■4-1 

m 

.S 



o 
o 



C 
*G 

'S 
+j 

t: 
o 

u 

o" 
'a 
O 



c 
c 
'G 

O 

00 

o 

4-) 
Wi 

o 
O 



c 

O 

U 
o 



a 

CO 



AUXILIARIES 341 



Heating the air for combustion is practiced to a considerable extent in 
marine work, with mechanical draft. In the Howden system the air is forced 
through the heater, while in the Ellis and Eaves system it is drawn through 
by the induced draft fan. 

Most of the applications in land service have been confined to municipal 
refuse destructors wherein forced draft fans or steam-jet blowers draw the 
air through the heater and discharge it into a closed ashpit, the tempera- 
ture rise being from 300 to 500 deg. 

When the air for combustion is heated 300 deg. or more, trouble might 
be expected from grate bars burning out more rapidly, and from excessive 
clinkering ; but this does not appear to be the case. 

When heat that would otherwise be wasted in industrial processes can 
be used to heat the air for combustion, the thermal efficiency of the whole 
plant is increased. In electric power plants it is becoming general so to 
utilize the heated air resulting from ventilating the generators, the air ducts 
being piped from the generators to the forced draft fan inlets. The forced 
draft air can be drawn from parts of the boiler room or from the space 
near industrial processes, space that otherwise might become unpleasantly 
hot, making for more comfortable operation and increased thermal efficiency. 



Auxiliary Engines and Turbines 

IN certain definite fields, according to /. S. Barstow, the small turbine is of 
conceded superiority, and in other fields the engine must hold sway. The 
following factors determine the adaptability, cost and economy of the equip- 
ment to be installed for any given service : 

A. — Maximum or minimum permissible speed, and whether the ap- 
paratus is driven at constant or variable speed. 

B. — Steam pressure (Initial and final) and superheat temperature, 
if any. 

C. — Power capacity of apparatus. 

D. — Space requirements of turbine and engine units, available room, 
power house construction, and cost of foundation or other sup- 
porting structure. 

E. — Use or application, if any, of exhaust for feed water heating, 
steam heating or process. 

F. — Available cooling water supply; If the turbine or engine Is to 
be run condensing, the temperature of the water and whether it 
must be artificially cooled and re-circulated. 

G. — Operating conditions, attendance, oiling, starting and stopping, 
vibration and noise. 

H. — Cost of complete installations. Including foundations, piping and 
condenser equipment, if any. 

Not until about 20 years ago was a practicable small turbine developed, 
and even up to ten years ago the turbine was looked upon mainly as an 
experiment. In the last few years, however, this type of prime mover has 
been built not only in small sizes, but also in 50,000 H.P. units for large cen- 
tral stations. The turbine therefore is as well developed as is the steam 
engine after more than one hundred years of improvement. 

Speed Limitation is of first importance in selecting the type of prime 
mover. Peripheral velocities must be high to utilize efficiently the energy 
of a steam jet in the turbine. Its water rate is lowest, therefore, when run- 
ning at a constant high speed. When speed variation or reversal is required, 
or when the speed is necessarily low, the engine is much better adapted to 
the service. 



342 




Erecting Two Heine Standard Boilers for the Caribbean Petroleum Co., 

San Lorenzo, Venezuela. 



AUXILIARIES 343 



If an engine is run at very high speeds, operating troubles are sure to 
be numerous, the upkeep is excessive, and the service unsatisfactory. The 
lack of driven apparatus designed to run efficiently at speeds consistent with 
high turbine economy has, in the past, frequently dictated the use of engines 
as prime movers. 

Speed reduction gears have been used with the turbine almost from 
the beginning of its commercial development. Recent improvements in high 
speed gearing, as well as in the manufacture of high speed direct-connected 
generators, blowers and pumps, running at 3000 r.p.m. and above, have 
greatly increased the possibilities for turbine installations. Direct-current 
generators as small as 10 KAV. capacity, and 60 cycle alternators of capacities 
as low as 150 KAV., designed for gear drive, are now obtainable. It is said 
that the increased efficiency of the higher speed turbine, and the saving 
effected in the generator construction by reason of the slower speed per- 
missible in the driven end, justify the expense and complication that the gears 
introduce. 

For power station work, where some of the auxiliaries are usually motor 
driven, the exhaust steam can be entirely condensed in the feed-water heater, 
and the water rate of the steam driven auxiliaries is not a limiting factor. 
Reliability, accessibility, low maintenance and labor costs are of more vital 
importance. Power station designers have always preferred, therefore, the 
turbo-auxiliary units, and there is now a decided tendency toward geared 
installations. 

Small engine units are run at high speeds, so that it is exceedingly 
difficult to keep them in continuous service, and almost impossible to secure 
smooth, quiet operation. The reciprocating units require close attention, and 
must be shut down, overhauled, and adjusted at frequent intervals; the cost 
of maintenance is high and breakdowns are by no means rare. An accident 
to a circulating or hot-well pump, for example, usually necessitates a shut- 
down of the main generator, with consequent loss of production, and in a 
public utilities plant, loss of prestige and the incurrence of public ill-will. 
In central stations, therefore, where the main units are few in number and 
of large size, the circulating, hot-well and boiler feed pumps are usually 
turbine-driven. 

For driving fans of large capacity at low pressures, say less than 1^ in. 
of water, for induced draft, hot air heating and ventilating systems, engines 
seem well suited. Fans built for this service run at less than 200 r.p.m., and 
are of the paddle-wheel type. In induced draft work, load fluctuation may 
require frequent changes in speed ; the engine is under the control of a 
throttling regulator, which is automatically actuated by a change of steam 
pressure. These conditions are unfavorable to turbine economy. 

The furnaces of underfeed stokers often carry air-duct pressures as high 
as 6 or 8 in. of water; the high speed multi-blade fan then makes the better in- 
stallatio», particularly when one fan serves several boilers. The size of the 
blower units would be excessive at speeds below 400 r.p.m., and the engine 
drive is uncertain and exi)ensive at this speed. Underfeed stokers at best 
can develop only from one-quarter to one-third their maximum capacity with 
natural draft, so that a blower breakdown under peak load is a serious matter. 
The ability of the turbine to stand up under the conditions justly entitles it 
to preference. 

Owing to the freedom from reciprocating motion, the foundations re- 
quired for turbines are small and light, there being little vibration to be 
absorbed when the machines are well aligned and balanced. The small sizes 
can be safely operated on floors designed for the ordinary loads. No diffi- 
culty is experienced with the transmission of vibration to the structural mem- 
bers of the building or to the piping" system. 



344 




d 

CO 

a 

CO 

IS 



V 



w 'o 



C as 

^ G 
S CO 

(h-i 

o o 

oc . 

rr- O 
•^ CS 

C 'm 
C w 

CJ '^ 

.— ■*-' 

u •" 

" e 

c 

V CO 



. "^ 
u 

CO 
CO 

a 
o 



AUXILIARIES 345 



The turbine is often used for boiler feed-pumps (centrifugal type) of 
more than 250 gal. per min. capacity, or about 3,000 boiler horsepower 
developed, and on account of its small size the layout is usually neater and 
more compact. When regulation by throttling is unnecessary, and the pumps 
run at or near capacity, the economy is better than that of the direct acting 
type. Valve renewal and packing troubles are avoided. The overload capa- 
city of the centrifugal type is small, so that the pump must be proportioned 
to meet the maximum demand, not the average boiler horsepower require- 
ments. In the smaller sizes, the cost of turbine units is high ; when the 
load fluctuates widely and the speed must vary, the economy is poor and 
it is better to install reciprocating pumps. 

The turbine possesses a great advantage in the simplicity of its con- 
struction, which tends toward increased reliability and lower cost of main- 
tenance. It can be started and loaded more quickly. In operation, it re- 
quires much less attention than an engine of corresponding capacity. The 
lubrication devices are few in number and of simple design. 

Applicability of Turbines. Summarizing the foregoing, the held of use- 
fulness of the turbine can be stated to be : 

1. — 'Direct-connected units, operating condensing. 60 cycle generators in all 
sizes. 

Direct-current generators up to 1000 K.W. capacit}', including exciter units 
of all sizes. 

Centrifugal pumps operating under substantially constant head and quan- 
tity conditions, and at heads say from 100 ft. up, depending upon the size 
of the unit. (This includes boiler feed pumps of more than 250 g.p.m. 
capacity, or 3,000 boiler horsepower developed.) 

Fans and blowers for delivering air at pressure from 1^ in. water col- 
umn to 30 lb. per sq. in. 

2. — Direct connected units, operating non-condensing for all the above pur- 
poses, when steam economy is not the prime factor, or when the ex- 
haust steam can be completely utilized, particularly if exhaust steam 
must be oil-free. 

3. — 'Geared units, operating either condensing or non-condensing, for all the 
above applications ; and for others where a steam engine is required on 
account of the slow speed of the driven apparatus. 

Applicability of Engines. The fields of usefulness of the engine are 
given as follows : 

1, — Non-condensing units, direct-connected, or belted and used for driving 
electric generators of all classes except exciter sets of small capacity, 
unless belted from the main engine. 

Centrifugal pumps, operating under variable head and quantity conditions 
and at low heads, say up to 100 ft., depending on the capacity of the 
unit. 

Pumps and compressors for delivering water or gases in small quantities 
and at high pressures ; pumps at pressures above 100 lb. per sq. in. and 
compressors at pressures from 1 lb. per sq. in. and above. 
Fans and blowers (including induced draft fans) for handling air in 
variable quantities and at low pressures, say not over 5-in. water column. 
All apparatus requiring reversal in direction or rotation, as in hoisting 
and traction engines. 

2. — Condensing units directly connected or belted, for all the above purposes, 
particularly when the condensing water supply is limited, and the water 
must be re-cooled and recirculated. 




Adflpina Hotel, Philadrfphia. Pa., cootaming four 255 H. P. 



347 



CHAPTER 10 



HEAT INSULATION 

THE function of a heat insulating material is to retard heat flow. It is 
heat insulation whether used to keep heat where it is wanted, as in a 
steam pipe ; or to keep heat away from where it is not wanted, as from 
the cold water in a drinking water line. 

Surface Resistance. The heat lost per degree temperature difference 
between steam and air from metal 1-in. thick, heated by steam on one side, 
and exposed to air on the other, is much less than the value of k shown for 
the metal because the temperature difference between surfaces, ti — tz, is much 
less than the temperature difference between steam and air, ^s — ^a. (See 
Fig. 175.) The air cannot take up the heat as rapidly as it can be trans- 
mitted by the metal; therefore, the temperature drop from the outside surface 
of the metal to the surrounding air is almost all of the total temperature 
difference between the steam and air. The drop through the metal, ti — 12, is 
only a small part of the total. The amount of heat transmitted per hour 
through unit thickness of material on flat surface \s k {f^ — t^). This hold- 
ing back of the heat due to the inability of air to take it up as quickly as it 
can be transmitted is called "surface resistance." 



Afefcr/- 




Fig. 175. Comparison of Heat Transmission from a Metal Plate, 1 inch 
Thick, when Insulated and Not Insulated. 



In good conductors of heat the greater part of the resistance offered to 
heat flow is surface resistance. In insulating material, however, most of the 



MS 



INSULATION 



resistance is in the insulation, and the surface resistance hs.? !e55 effect on 
the amount of heat transmitted. 

The surface resistance of a surface su: : tr^f 
pared with that of one exposed to air. A p:^e s:: 
fore transmit a vastly greater amount of hei: 
rounded by air, even though the ir.terr.al ccriu 
same for each pipe. 

Losses from Bare Heated 5 7: ;: 7 r r 1. Fig, 176, shows the rate 
of heat loss at various tempera: ure iifitre .;ti r:ween hot surface and sur- 
rounding air. Curve 2 shows the total heat loss at any particular tempera- 
ture difference. Ordinates for curve 1 are on the left, and for curve 2 on 
the right of the chart. 



. water is small as com- 
rred in water will there- 
ir. :he same pipe sur- 

::v of the metal is the 




iOO 200 ^ 500 

Tzmp.Diff. b>ctween Hot Surface and Surrouroiro 



500 



'.^^z-zzs 



Fig. 176. Comparison of Rate of Heat Loss at Various Temperatrire 

Differences and at a Constant Temperature Difference. 



INSULATION 



349 



Table 44, for different steam pressures and temperatures, shows the heat 
lost per year from a square foot of heated surface, the amount of coal re- 
quired to replace these losses and the square feet required to waste a ton 
of co^l per year. 

Table 44. Heat Losses from Uninsulated Hot Surfaces. 



Steam 

Pressure 

(Gage), Lb. 



Steam 

Temperature, 

Degrees 



Temp. Difif., 

Steam and 

Surrounding 

Air, Degrees 



Heat Loss 

per Sq. Ft. 

per Hr., 

B.t.u. 



Pounds of Coal 
Wasted per 
Year per Sq. 

Ft. of 

Uninsulated 

Surface 



Sq. Ft. of 

Surface 

Wasting 

1 Ton of Coal 

per Year 





10 
25 



212 
240 

267 



142 
170 
197 



334 
425 
522.5 



293 
372 
458 



6.82 
5.38 
4.37 



50 

75 
' 100 


298 
320 
338 


228 
250 

268 


644 

737.5 

820 


564 
646 
718 


3.55 
3.10 
2.79 


150 
200 
250 


366 
388 
406 


296 
318 
336 


960 
1,079 

1,184 


840 

945 

1,036 


2.38 
2.12 
1.93 


Temperatures Below 212 Degrees. 



Surface 

Temperature, 

Degrees 



Temp. DiflF., 

Surface and 

Surrounding Air, 

Degrees 



Heat Loss per Sq. 
Ft. per Hr., B.t.u. 



Pounds of Coal 

Wasted per Year 

per Sq. Foot of 

Uninsulated 

Surface 



Sq. Ft. of Surface 
Wasting 1 Ton 
of Coal per Year 



100 
120 
140 



30 
50 
70 



56.6 

97.5 

142.0 



49.6 

85.4 

124.3 



40.3 
23.4 
16.1 



160 
180 
200 



90 
110 
130 



190.0 
242.0 
298.5 



166.3 
212.0 
261.5 



12.03 
9.44 
7.65 



Above figures based upon 10,000 B.t.u. available per pound of coal, which is equivalent to a 
boiler efficiency of 70 per cent, the heat value of the coal being assumed as 14,000 B.t.u. per pound. 
The temperature of the "surrounding air" is 70 degrees in both parts of the table. 



At 100 lb. pressure, less than 3 sq. ft. of bare surface are required to waste 
a ton of coal in a year. An area greater than this is exposed when a pair 
of 10-in, flanges is left uninsulated. Also, many surfaces at low temperatures 
are left uninsulated on the ground that the temperature is not high enough to 
justify insulation. Table 44 shows, however, that only 12 sq. ft. of surface 
at 160 deg. are required to waste a ton of coal per year. Surfaces too hot to 
be touched with comfort represent a loss of heat. Fig. 177 shows the saving 
by the use of a good insulation. 

Value of Heat Insulation. Heat insulation saves fuel directly or in- 
directly; in addition, insulated equipment renders better service, working con- 
ditions near heated surfaces are more comfortable, and the safety from fire 
and accident is greater. 

Insulation cannot prevent the flow of heat completely, as it does the 
flow of electricity. All substances conduct heat to some extent. Table 45 



350 




V 

O 
CO 



il 



U 7 

'c vT 



o 

s ^ 

X V 

OH 



1- (X, 

o 



INSULA TI ON 



351 



shows how much lower the conductivities of some materials are than those 
of others and therefore indicates wliich should he good insulators. 




50 100 150 200 e50 300 350 400 450 

Difference between Pipe oind Room Temperatures, Degrees 

Fig, 177. Heat Loss from Bare Steam Pipe and Saving Effected by Good 

Insulation Covering. Lines A and B show Saving per Degree 

Difference is Much Greater at High Steam Temperatures. 

Couduclivitics of Materials. Tiihh 45 shows the conductivities of com- 
mon materials. The conductivity, k, is expressed in B.t.u. per square fool 
per degree temperature difference hetween surfaces per inch thickness per 
hour. 

Requirements of Good Insulation. In order to he satisfactory, an insula- 
tion must withstand the temperature and the wear and tear imposed upon 
it. The mechanical form must permit its application in workmanlike manner 
to the surfaces to he insulated. The insulation must he durahle and must 
he efficient in preventing heat flow. Insulating materials of laminated fihrous 
structure arc considered more durahle than molded forms of insulation. 



352 




c 

O 
O 

d 
O 



K 



3 2 

CO D 

"I 

O >> 

^^ 

O O 
J3 O 

•M t-i 

U. r" 
D 

:;: G 
o -^ 

PQ CO 

CO O 
CD 



C/3 

.s 



CO 
0) 

H 



INSULATION 



353 



Table 45. Conductivities of Materials. 



Material 



Temperature, 
Degrees 



Conductivity, 

(k) 



Silver 

Silver 

Copper 

Copper 

Aluminum 

Aluminum 

Pure Iron 

Wrought Iron 

Steel (Soft) 

Cast Iron 

Coal* 

Granite •. 

Ice 

Marble 

Limestone 

Sandstone 

Soil (Wet) 

Soil (Dry) 

Firebrick 

Concrete (Stone) 

Concrete (Stone) 

Concrete (Cinder) 

Glass 

Brickwork 

Water 

Sand (White, Dry) 

Wood— Maple 

Wood— Oak 

Wood — Yellow Pine 

Wood — White Pine 

Diatomaceous Earth Blocks 

Air Cell Asbestos 

85 percent Magnesia 

Asbesto-Sponge, Felted 

Cork 

Hair Felt . . 

Air (True Conductivity, Radiation and Convection 
eliminated) ** 



64 
212 

64 
212 

64 
212 
212 
212 

212 



,800 



1,000 

300 

300 

300 

50 

50 



2,920 
2,880 
2,667 
2,638 
1,393 
1,428 
439 
412 
322 
314 
23.2 
20.0 
16.5 
15.0 
15.0 
14.5 
10.7 
2.55 
9.0 



0.50 



7.8 

6.38 

2.35 

7.0 

5.0 

4.35 

2.7 

1.17 

1.04 

1.0 

0.83 

0.85 

0.72 

to 0.55 

0.468 

0.35 

0.30 

0.18 



In the materials from Diatomaceous Earth to Hair Felt, inclusive, the temperatures are the 
differences between surfaces. When the temperature is not stated in the table, it is understood 
to be at or near that of the ordinary room. 

*Carbon, in its various forms, h,a3 conductivities varying between extremely wide limits. 
Some forms of graphite have conductivities from 10 to 20 times as great as that given above for 
coal, while powdered charcoal has a conductivity only about l/30th that of coal. 

**Radiation and convection are the largest factors in the transmission of heat through 
open air, conduction being comparatively insignificant. The true conductivity is approached 
only when the air is confined in minute cells, and the effects of radiation and convection are 
minimized. 

Practically all commercial insulations depend upon entrapped air for 
their insulating value. Air has a low heat conducting power (see Table 45) 
and if confined in small spaces to minimize the effect of convection within 
the spaces, and of radiation of heat across them, the resistance to heat flow 
is high. Even perfect vacuum would be ineffective in preventing heat flow 
unless the bounding surfaces were mirrored to prevent radiation. 



354 



lATION 



La Fig. 178 the heat losses tliFcmg^ diflFerent commercial m s i ^PafiTig mate- 
rials are compared. Table 46 shows the tibi<^nesses and weights per lineal 
foot of the materials referred to in Fig. 178. The nses for which materials 
~e"fed by mannfacttirers ire also grren. 



re: 



O-S-I 



t- 0.8C 



a45 



a4€ 



p.-zn 



III / 


! t 1 1 ^^ / 






<. 


^ 


^ 


/ 


/ 


/ 


/ 






/ 


^ ^-^ ,/ y .^ 




^ 


^ 








-X 




v^ 


X 




>X^ 






\ 

1 








y \ 


<'^ 




A. 


y 


^^""^ >• 










^ V 


'yi''^ 




^ 


^ 


^ 


^ 

y 






^ 


^ 


— 


-— 




5-^^^^^ - - 


■^ 


^ 

^ 


> 




^^^-^ 






,- -^ 


-s=* 




^ 




^ 


-f^r 










^ 


^ 


iic: 




-.- < " 


' ' '^^ 1 * 


^' " 


f 






i^ti==^ 







-r"^^,^ 


-" . 







-.- '^..-^^^ - ■ ' ' ' ' 


^^ — " . 




^^_ 




-■^ ^- 






fe 


-^ 


^ 


^ 




=== 




— - 


'< 


''" 


■^^ 


^-■^ 


•^^ 


-:; 


::^ 


^^ 


■ ^ 






-f'-- 








i 


i! [ 1 1 ; i 



500 



( PipeTempe' - - . 'f - - : - ~ - .e ' 

Fig. 1 78. Comparison of Heat Loss Through Different 
Insulation Materials. 



Materials for Insvlaticms. Asbestos, Fig. 179. is the most important of all 
materials nsed as insulations at steam temperatures. Many insulations con- 
sist almost oitirely of asbestos^ and on account of its fibrous form asbestos 
is used as a binding material in almost every insulation manufactured for 
high temperatures. 



INSULATION 



355 



Table 46. Thickness and Weight of Insulating Materials, 



Test No. 



Material 



Thickness, , 

Inches L, ^ ' 

Lb. per 



Actual 



Appar- Lin. 
ent Ft. 



Recommended for 



I 

II 

III 

IV 

V 

VI 

VII 

VIII 

IX 

X 

XI 

XII 

XIII 

XIV 

XV 

XVI 

XVII 

XX 

XXIV 



0.9S 



1.25 



J-M 85 per cent Magnesia. . 1 . 11 

J-M Indented 

J-M Vitribestos 

J-M Eureka 

J-M Molded Asbestos 

J-M Wool Felt 

Sal-mo Expanded 

Carey Carocel 

Carey Serrated 

Carey Duplex 

Carey 85 per cent Magnesia. 

Sal-mo Wool Felt I 

Nonpareil High Pressure ' 1 . 16 

J-M Asbestos Fire Felt . 99 

J-M Asbesto-Sponge Felted.. 

J-M Asbestocel 



0.99 

1.00 

.96 

1.10 



J-M Air Cell 

Plastic 85 per cent Magnesia. 
Sal-mo Air Cell 



00 
05 



1.18 
1.12 
1.11 
1.04 
1.26 
1.10 
1.07 
1.06 
1.13 
1.01 
1.19 
1.01 
1.23 
1.09 
1.16 
1.10 

1.11 
1.05 
0.95 



2.73 
3.46 
4.05 
4.60 
5.53 
2.59 
3.47 
3.06 
5.66 
1.79 
2.74 
3.73 
2.96 
3.75 
4.04 
1.94 

1.55 
3.33 
1.57 



High pressure steam. 

High pressure steam. 

Stack and breeching linings. 

Low pressure steam and hot water. 

Low and medium pressure steam. 

Low pressure steam and hot water. 

High pressure steam. 

Medium and low pressure steam. 

High pressure steam. 

Low pressure steam and hot water. 

High pressure steam. 

Low pressure steam and hot water. 

Highpressure&superheated steam. 

Highpressure&superheatedsteam. 

High pressure & superheated steam. 

Medium and low pressure steam 

and hot water. 
Low pressure steam andhot water. 
Fittings and irregular surfaces. 
Low pressure steam and hot water. 



*Apparent thickness is distance from pipe surface to outer surface of insulation. 

Chemicall}', asbestos is a hydrated silicate of magnesia. A typical analysis 
is given below : 

Per cent. 

Silica (SiOJ 41.0 

Magnesium oxide (MgO) 41.5 

Ferric oxide (FejOa) 3.0 

Aluminum oxide (AlaO:;) 0.9 

Water (H,0) 12 to 14 

Asbestos, although highly heat resisting, has little insulating value in 
its natural rock form (see Fig. 179). Not until the hbers are separated and 
manufactured into felts, in w^hich they entrap a large number of finely divided 
air spaces, does asbestos become an efficient insulating material. 




Fig. 179. Rock Asbestos. 







^ 





c 


^ 


■r^ 




WO 


4-) 


- 


o 


■*j 










i^ 


2 


Q 


o 




f^ 


u 




> 


U 


o 


*■ 







CJ 


U 


K 




•T. 


CO 




^ 


— 


ffl 


o 




m 


^ 


-a 


^ 






w 


o 




0) 


^ 





CS 


"— > 


•^ 


^ 


m 


a 






o 

V 



INSULATION 357 



Asbestos will withstand temperatures up to about 1500 deg,, but the 
fibers become brittle when subjected continuously to temperatures above 
1200 degrees. The limit for the fire-felt type of asbestos insulation, which 
consists principally of asbestos fiber and a binding material, is about 1200 de- 
grees. The limiting temperature for laminated forms of asbestos insula- 
tion is about 700 degrees. The limit for the cellular types of asbestos insula- 
tion is about 300 deg., on account of the organic matter used in the asbestos 
felt from which they are built. 

Carbonate of Magnesia. Next in importance to asbestos is hydrated 
magnesium carbonate [4MgC03. Mg(0H)2. 5H2O]. This material in the 
form manufactured for insulating purposes is light and porous and has good 
insulating value. The necessary mechanical strength and durabiliiv are 
secured by mixing about 15 per cent of asbestos fiber and 85 per cent of 
hydrated magnesium carbonate ; from this the name "'85 per cent magnesia'' is 
derived. 

The natural rock from which the magnesium carbonate is obtained is 
hard and dense, resembling marble. In this original form the material has 
practically no insulating value. The high insulating value of 85 per cent 
magnesia is due to the process of manufacturing. The magnesium carbon- 
ate is separated from the other ingredients in the original stone, the finished 
product having one-tenth of the density and less than one-twentieth of the 
conductivity of the natural rock. 

The 85 per cent magnesia is not adapted to temperatures above 500 
degrees. At higher temperatures the material is calcined, loses CO2, shrinks 
and loses strength rapidly. 

Diatomaceoiis Earth (Kieselgiihr) is a naturally occurring mineral of 
high heat resistance. It consists of practically pure silica (Si02), which is 
finely divided, owing to the manner in which the deposits were built up under 
water in prehistoric times from the skeletons of microscopic organisms 
known as diatoms. 

The insulating value is less than that of asbestos or magnesia, but it 
will withstand higher temperatures than either of these materials. In molded 
forms it is usually strengthened by being mixed with asbestos fiber. Blocks 
manufactured from diatomaceous earth will withstand temperatures up to 
2000 degrees. 

Cork. For the insulation of larger surfaces at low temperatures, as in 
refrigeration work, cork is the most desirable material. The source of cork 
is the bark of the cork oak tree. The cork is ground and molded into 
sheets by the application of heat and pressure. No binding material is re- 
quired as the natural gum of the cork cements the particles firmly, and serves 
as a moisture proof coating as well. The use of cork is confined almost 
exclusively to refrigeration and cold storage work. 

Flair Felt. This has the highest insulating value of any commercial 
insulating material. It is widely used for the insulation of brine and cold 
water pipes, and is then sealed in with waterproof membranes to prevent 
access of moisture from the air. 

On outdoor steam lines, hair felt is also used outside of other insula- 
tions. The inner layer of asbestos or magnesia protects the hair felt from 
the high temperatures, while the high insulating value of the hair felt in- 
creases the efficiency of the combination. The maximum temperature to 
which hair felt can be subjected is about 250 degrees. 

Miscellaneous Materials. Wool, silk, and cotton have insulating value, 
but this is principally used in clothing. Wood and paper are of value as 
insulations, and are used in building construction. 




o 
*j 
03 

u 

■4-) 

OS 

u 

o 

c 

"5 



Ud 



6 s 

•So 

•c.S 

"SCQ 
a 

'1 5 



-a 

c 

GO 

09 

v 

C 

"C 



(U 



00 

o 



INSULATION 



359 



Heat Transmission Through Insulation. 

The factors in determining the rate at which heat will be transmitted 
through miit area of an insulating material are : 

(13 The conductivity of the material, 

(2) The temperature difference between its two surfaces, 

(3) The thickness of the insulation, 

(4) The form of insulated surface. 

Of lesser importance are the finish of the surface and the velocity of 
air currents over the surfaces. 

Table 45 shows how greatly the conductivities of materials vary. The 
figures in the table are surface-to-surface conductivities. Fig. 178, however, 
compares approximately equal thicknesses of insulating materials, the ordi- 
nates being actual rates of heat transmission per square foot per hour per 
degree temperature difference between hot surface and surrounding air. 



1-2 































































I 








































I 








































! 




















\ 




np Diff 


'SOODe 


9- 












\ 


i 




















\ 


300 L 


eg. 
















\ 


\ 




















^ 


\ 




>g. 
















^V 




^ 


^ 


--_. 



























2 3 

1 hickness, Inches 



Fig. 180. Effect on Heat Transmission from a Flat Surface of Various 
Thicknesses of Insulating Material. 



360 



HEAT 



Effect of Temperature on Heat Transmission. Fig. 180 shows that the 
rate of heat transmission per degree is not the same at all temperatures. 
However, the loss at any temperature can be found by muhiplying the 
transmission factor given in the chart for any temperature difference 
between hot surface and surrounding air, by that temperature difference. 

Efficiency. Insulations are often compared in terms of their "insulating 
efficiencies." As thus used, the term "efticiency" is the percentage of the 
uninsulated surface loss saved by a given insulation. It is bare surface 
loss minus loss from insulated surface, divided by bare surface loss ; both 
losses apply to the same area and are for the same temperature difference. 

Thickness and Heat Transmission. Fig, 180 shows the variation of heat 
transmission from different thicknesses of material on flat surfaces. The loss 
through material 2-in. thick is greater than one-half of that through material 
1-in. thick, even though the figures are for flat surfaces, for which the re- 
sistance of the 2-in. material is exactly double that of the 1-in. material. 
The "surface resistance" is practically the same for the 1-in. as for the 2-in. 
thickness. Consequently, the resistance of 2 in. of material plus one surface 
resistance is not double that of the 1 in. of material plus one surface re- 
sistance, and heat transmission is inversely proportional to total resistance. 



■ D 


1 j 


< ! 






















CO 








5\ 




















Q 

cL 








^ 


1 

1 
















«s0.4 


- 






\ 


V XV 




V 


















I- 

CI 










N 


n:^ 


<^ 


^:::;^ 
























\ 




■v 






& 

to 
















1 ^^^"**~«^^/~'~" 

: 


I^ 300 


\ Ter 


np. Di'ff 
grees 




































V) 

or 


































C 



































Thickness, Inches 

Fig, 181. Effect on Heat Transmission from a Pipe Surface of Various 
Thicknesses of Insulating Material. 

Fig, 181 shows the effect of the thickness on heat transmission for pipe 
surfaces. The loss through material 2-in. thick is even more above one-half 
of that through the 1-in. thickness, than it was for the flat surfaces. In 
addition to the surface resistance effect, the second inch of insulation is 
applied over a larger area than the first inch, so that it does not offer as 
much resistance to heat flow. 

Pipe Size and Heat Transmission. Fig. 182 shows how the rate of heat 
transmission through a given thickness of insulation varies with pipe size. 
By comparing this chart with Fig. 180. the losses through different thicknesses 
on pipes are found to be greater than through the same thickness of the same 
insulation on flat surfaces ; also, as shown in Fig. 183. the losses are greater 
on small than on large pipes, other factors being the same. 



INSULATION 



361 



08 



0.7 



0.6 



g-05 



'0.4 



S0.3 



hQ2 





















































\ 
















































\ 
















































\\ 
















































\\ 


\ 














































\\ 


\; 


\, 












































^ 


^\ 


s 


\ 


k^, 








































V 




\ 


-V, 


■^ 


^ 


^ 


^ 


A 


9DWlol ' 




























\ 


^> 


N 






.^ 














\'ll£5 


5 /" 
























\^ 


<^ 






.^^ 




" ■ 




~~~~ 








/'/2 


' 
























\ 




C::- 


■-^ 


, 











. 




\ 


























^ 




"~~~ 


^- 


— 












=^ 


iS- 


































■ ■ 


•— -^ 









4" 















































































































































































)123456789 10 II 

Nominal Diameter of Pipe, Inches 

Fig. 182. Comparison of Heat Loss from Various Sizes of Pipe. 



12 



In flat surface insulation all the heat flows straight through in parallel 
lines, but in pipe insulation the heat has a continually widening path into 
which to spread as it flows outward. Consequently more heat will flow from 
a given area of pipe surface than from the same area of flat surface. The 
smaller the pipe the more rapidly the path for heat flow spreads out ; there- 
fore the greater is the rate of heat loss for a given pipe area and thickness 
of insulation. 





Fig. 183. Relative Heat Loss Through Flat and 
Curved Surfaces. 



Air Currcn\s and Surface Finisli. Air currents greatly decrease the sur- 
face resistance. With bare surfaces the losses can be increased by the efi^ect 
of wind to several times the values in still air. When efficient insulations 
are applied so that they are sealed against the effect of air blowing through 
the joints, the maximum increase in heat transmission due to wind velocity 
varies from about 10 per cent for an insulation 3-in. thick to about 30 per 
cent for a 1-in. thick insulation. These figures are only approximate, 
because the more efficient the insulation, the less affected it is by wind 
velocity. 

If the insulation is loosely applied so that air can circulate through the 
joints and crevices or between the insulation and the pipe, wind can in- 
crease the loss upward of 100 per cent. Painting the surface of insulation 
usually decreases the loss of heat slightly and is desirable because the sur- 
face is thus sealed against circulation of air. 



Z61 




o 



T3 . 

'Z ^ 

■^ o 



1^ 

w r 
o 

U 

i.i: 

C u 

C. O 

."^ V 
ffl *- 



V 

C 

*C 
X 

Cm 
O 

o 
o 
o 



INSULATION 



363 



Thickness of Insulation. The thickness it will pay to use depends upon: 

(1) The temperature difference between hot surface and air, 

(2) The value of the heat units to be saved by insulation. 

(3) The size of pipe, 

(4) The kind of insulation used, 

(5) The cost of insulation. 

The last increment of insulation put on should save enough to pay a 
good return on its cost. The minimum allowable return is usually taken at 
about 14 per cent, which covers interest and depreciation. 



<o4 













1 
































Sfec 


'ma 


'20 


'.enfi. 


per 


1.000.000 


em 


























































fla 


i-^ 


^ 
















r^ 


^ 










^ 




^ 


^ 


^^ 






^ 


^ 


-^ 






^ 


9> 

5/4" 


-= 


^ 


^ 


S^ 


^ 


1^ 






— 











































(^4 



i?3 













































Sfec 


•ma 


'40 Cent 


s per 1,000,000 


B.TM. 




















^ 












f 


^ 


"^ 


, ^ 


^ 








^ 






l^ 


<^ 




-^ 






/ 






^ 




^' 




^ 


/ 


/' 


,^ 




,^ 


^ 


^ 


II 




^ 


/ 




^^ 


^^ 




^ 


""^f^ 






-y. 


^ 


>: 




^ 


-^ 


^^ 

















































100 200 300 400 500 600 100 200 300 

Temperature Difference, Degrees 



400 



500 600 



5(f3 

























steam at 60 Cen 
not- innnnnh r t 


fs 






^ 


'^ 


pe^ 


' 






^y 




^ 




^ 










^ 


r\ 




^ 




^^ 






/ 


/ 


> 


^ 




^ 


'^ 


^ 




y 


/ 


^ 


\ 


^ 




"^ 


^ 


^ 


/ 


'a 




^ 
^ 




> 








^ 


'/ 


A 


^ 




y 


^% 


f>- 


-^ 




^ 


/> 


:; 


y' 


,^ 


-^ 


^^ 


i\^ 


^ 


^^ 




'y 




^ 




^ 


^ 



















































C94 



10 7 



f^2 















^ 


^ 


^- 






steam af 80 C 
Lnor- in/vinm R 


enfs 

Til 


y 


y 








per 


' 'i 

\ y 


^ 


y 


^ 






^ 






Oy 


A 


y 


y" 






^ 




/ 




A 




^ 




_.^-- 


^ 


/ 


/ 


A 


/ 

1 w 


y 


[y 


^ 






^^ 


9 


\/ 




ApA 


^ 






^ 


y 


y 


y 




y\ 


■^1 






/ 


'A 






215 


^ 










>^ 


> 


A 


.>' 























































100 200 300 400 500 600 100 200 300 

Temperature Difference, Degrees 



400 



500 600 



Fig. 184. Chart for Determining Most Economical Thickness of 
85 Per cent Magnesia. 




V 

'C 



u 



INSULATION 365 



Fig. 184 is a chart for determining the most economical thickness of 85 
per cent magnesia. It can also be used in selecting the thickness of other 
materials. However, the actual saving should be checked to determine 
whether the return on the investment is satisfactory. 

The data given in Figs. 178 to 184 can be used to determine the most 
economical thickness of insulation, as follows : Required to find whether 2 
or 2^<2 in. thickness of asbestos sponge felted insulation should be used on 
a boiler drum. Steam pressure is 150 lb. gage; cost of coal, $5 per ton; 
cost of insulation, 30 cents per sq. ft. 1 in. thick; boiler room temperature, 
80 degrees. (All heat losses and savings are expressed in B.t.u. per de- 
gree of temperature difference.) 



Steam temperature at 150 lb. gage pressure 366 

Room temperature 80 

Temperature difference 286 

Heat loss per sq. ft. per hour through 2-in. thick asbestos sponge felted 

(Fig. 180) 0.21 

Heat loss per sq. ft. per hour through 2^ in. thick asbestos sponge 

felted 0.17 

Saving per sq. ft. per hour per deg. temp. diff. by use of 2f-2-in. thick- 
ness - 0.O4 

Saving per sq. ft. per hour = 286 X 0.04 = 11.44 

Saving per sq. ft. per year = 8760 X 11-44 = 100.300 

Saving in lb. of coal per sq. ft. 

100.300 i^n-2 

per year =: 10.03 

10,000 
Saving in dollars per sq. ft. 

per year _10^y $5.00 = 0.025 

20000 ' 

Cost of 2y2 in. insulation per sq. ft. = lYz X 0.30 = 0.75 

Cost of 2 in. insulation per sq. ft. = 2 X 0.30 ^ 0.60 



Cost of additional ^ in. of insulation ^=- .._. 0.15 

Above saving expressed as percentage return on 

additional cost lOOX^^ = 16.7 

0.15 

This is a satisfactory return so that the use of 2>2 in. thick insulation is 
a paying investment. 

(On such surfaces as boiler drums and heaters, the >4 in. of insulation 
is usualh" applied in the form of a plastic insulating cement.) 

In like manner, Figs. 182 and 184 can be used to check the most 
economical thicknesses of pipe insulations. 

Insulation of Boiler Drums and Piping. In insulating steam and hot 
water pipes and boiler drums, the correct thickness (see Fig. 184) should be 
applied so that there are no crevices or open joints. Asbestos cement can 
be used to seal openings, and a layer of asbestos cement can be applied over 
the outside of sheet or block insulation, to give a smooth hard finish. 



366 




u 


, 










o 


, 


m 


CO 


•a 


V 


CO 
T5 


o 


C 

CO 

■♦J 


C 


C/3 


(U 


<u 


w 


G 


<4-r 


(U 


O 


K 


0.' 


bD 




C 


X 


O 


o 
o 
o 


l/i 


c-~ 


6 


•o 


U 


m 






TJ 


CO 


CO 


CO 


<U 


C 


J 






CO 


^ 


CO 


CXSi 


(U 




(/) 


>1 


o 


CO 


CO 


S 




o 




U 


4-> 








n 


^ 




H 


<4-l 




C 




CO 


. 




CO 


Oh 


u 


• 


^ 


o 


o 


^ 


4-1 


«^ 




CO 


a) 


<u 


-M 


C 


CO 


• 1-4 


u 


^0 


t-i 


C 


(L) 
> 


CO 


P:JU 


(U 


c 


x: 


(U 


+j 


(L> 




U 


'o' 





e 


u 

V 


o 


> 


o 


o 


;^ 


■M 




(U 


u 


CO 


<u 












o 




CQ 





INSULATION 367 



Boiler Wall Insttlation. By insulation of boiler walls about one-half of 
the heat transmission through them can be prevented. This saving alone 
would make the insulation pay, but the saving can be still larger if the in- 
sulation seals the wall effectively against air injfiltration. To accomplish this 
the insulation should be applied in large sheets and finished on the outside 
with about ^ in. of asbestos cement. 

The application of insulation on the outside of a brick wall is quite 
different from applying it to a steam-heated surface at the same temperature. 
The steam-heated surface remains at about the same temperature as it was 
before the insulation was applied; for the temperature is only a little below 
that of the steam. On the other hand, the blanketing effect of insulation 
holds the heat in the brick wall. The temperature of the wall surface is 
greatly increased, the outer surface of the wall being at a temperature far 
below that of the source of heat. This temperature increase may amount 
to 500 deg. on the portions of the wall opposite the furnace, varying with 
the thickness of wall and the thickness and kind of insulation. Consequently 
an insulation more than 90 per cent efficient on a steam-heated surface saves 
only from 40 to SO per cent of the heat radiated from a brick wall. The 
insulation itself is not any less efficient, but the difference is due to the 
increased temperature of the wall surface. 

Reference should also be made to Chapter 4 on FURNACES AND 
SETTINGS. 

Breeching Insulation. If the breeching leads directly to the stack the 
heat saved by insulation does not find its way into the steam. However, the 
draft is increased when this heat is retained in the gases. With an econo- 
mizer the heat is returned to the boiler. Insulating the breeching helps to 
cool the boiler room, which otherwise might be unbearably hot. 

Breechings are insulated either by an inside lining or by insulation ap- 
plied to the outside surface. An inside lining, finished with a coating of re- 
fractory cement, protects the steel. On the other hand more efficient insula- 
tion can be used on the outside of the breeching, and then does not obstruct 
the draft area. 

Overhead Outdoor Lines. When outdoor lines are run overhead they 
can be insulated with the same materials used on similar lines indoors. The 
insulation must be thicker on account of the lower temperatures and the 
exposure to wind. (See Hair Felt.) It must also be protected from the 
weather by sheet iron or asbestos roofing jacket. Hair felt, with an inner 
lining of asbestos or magnesia, is used successfully for outdoor lines. 

Underground Lines in tunnels can be treated just as if they were indoors, 
except that the canvas must be thoroughly painted as a protection against 
moisture. 

Lines running in covered trenches should be treated in the same manner 
as overhead outdoor lines. 

Lines running underground can be insulated by enclosing them in vitrified 
tile conduit and placing an efficient filling material in the space between 
the pipe and tile. All joints must be sealed. Thorough drainage must be 
provided by a tile underdrain and crushed stone, which should be brought 
well above the center-line of the conduit. 

Cold Water Lines. These can be insulated with hair felt or cork. Mois- 
ture condenses easily from the air on a cold pipe, and the moisture greatly 
reduces the insulating value. Therefore, all insulations on cold water lines 
should be so thoroughly sealed that moisture-laden air cannot penetrate them. 



368 




o 
X 

o 

o 






OS u 



o 



c 
o 
WW 



^ (U 



CO bi 

•go 

o > 

U o 



^:^ 
oPQ 

ol 

u 

a 
PU 

c 
o 

•4-< 

c 



CO 



369 



CHAPTER 11 



HEAT AND COMBUSTION 

Theory of Heat 

HEAT is a form of energy convertible in exact quantitative relations into 
other forms of energy. When two bodies at different temperatures are 
placed in communication, the temperature of the warmer body falls while 
that of the colder rises until the two bodies attain the same temperature. To 
account for this phenomenon, we say that heat flows from the hotter to the 
colder body. The fall of temperature of the one is due to a loss of heat, 
while the rise in temperature of the other is due to a gain in heat. 

In the caloric theory, heat or caloric was assumed to be a fluid which 
could flow from one body to another and thus cause changes of temperature. 
But the experiments of Rum ford, Dav\', and Joule invalidated the old caloric 
theory and established the modern mechanical theory. 

Heat may be generated by the expenditure of mechanical work, by 
chemical reaction, or by the electric current. Familiar examples are the 
heating of bearings due to friction, the heat generated by the combustion of 
coal, and the heat produced in an electric lamp filament. 

Useful work can be done by the expenditure of heat, as in the steam 
engine. The law of definite relationship between work done and heat ex- 
pended has been firmly established by the experiments of Joule. According 
to Joule, heat is not a fluid substance like caloric, but is a form of energy due 
to the motion or configuration of the molecules in a body or system. 

Thermometry 

T~'HE measurement of the quantity of heat abstracted from or added to 
^ a body depends primarily upon the measurement of temperatures ; that 
is, upon thermometry. The temperature of a body is a measure of the 
intensity of its heat, or its ability to impart heat to cooler bodies or to 
abstract heat from warmer ones. 

Temperature is expressed in units called degrees, whicJi are subdivisions 
of the temperature range between the temperature of melting ice and that 
of boiling water. There are three temperature scales in use ; the scale of 
Fahrenheit, which is used in nearly all engineering work ; that of CelsiiiG, 
called the Centigrade scale, which is used generally in scientific laboratory 
work; and that of Reaumur, which is used to some extent in Europe. 

The Fahrenheit scale is practically the only one used in American power 
p]ant practice. When no scale is mentioned in this book, the temperatures 
are given in degrees Fahrenheit. 

Conversions of temperature readings from one scale to another are quite 
simple, as may be seen from the following table : 



370 



HEAT 





Table 47. 


Temperature Scales. 




Explanation 


Degrees 
Fahrenheit 


Degrees 
Centigrade 


Degrees 
Reaumur 


Freezing Point 

Boiling Point 


32° 
212° 
180° 
9 


0° 
100° 
100'' 

5 


0° 
80° 


Difference 


80° 


Ratio of Difference 


4 



Conversions are made as follows : 



(CX 4- )+^2 = F 

(RX 4- )-T^2 = F 
4 

(F-32) X -g- =^ 

RX -^ =^C 

4 

{F-3Z)X -^ =R 
CX 4- =R 



(30) 
(31) 
(32) 
{33) 
(34) 
(35) 



Absolute Temperature 

INVESTIGATIONS with gases show that as they are cooled the pressure 
they exert is diminished uniformly. The temperature at which the pressure 
would vanish is called "absolute zero." This point, which has been closely 
approached in practice, is expressed as — 460 deg. Fahr. The "absolute 
temperature" of a body is therefore its temperature above absolute zero, 
that is, the regular scale reading plus 460, and is often used in calculations 
relating to expansion and radiation. 

Thermodynamic Temperature Scale 

"T^HE only standard of temperature which depends solely upon the nature 
■^ of heat and is independent of the nature of any measuring substance is 
the "Thermodynamic Temperature Scale." By this scale, the ratio of any 
two temperatures is equal to the ratio between heat absorbed and emitted 
liy a reversible thermodynamic engine working between the same tempera- 
tures. Again, these temperatures are numerically equal to those that would 
be indicated b}' an ideal gas thermometer, obeying exactly Boyle's law, 
PV = RT. Constant-volume gas thermometers, employing gases whose devia- 
tions from the properties of perfect gases are known, are used, therefore, to 
calibrate instruments for actual temperature measurement. Hydrogen is used 
for calibrating when the temperatures do not exceed 600 degrees. From 6(K) 
to 2800 deg. nitrogen is preferable, as it has less tendency to diffuse 
through the walls at the higher temperatures. The temperatures are observed 
as functions of the pressure increment, and a calibration thus determined 
for simpler forms of thermometer exposed to the same temperature. 

Thermometers and Pyrometers 

FIXED points have been determined by comparison with standard gas 
thermometers, and are used in calibrating instruments for high tempera- 
ture readings. These are expressed in degrees Fahrenheit as follows : 



HEAT 



371 



Table 48. Fixed Points. 

Substance 

Naphthalene boils at 760 mm. (29.92 in. of mercury) 

pressure 

Benzophenone boils at 760 mm. pressure 

Cadmium melts or soHdifies in air 

Zinc melts or solidifies in air 

Sulphur boils at 760 mm. pressure 

Antimony melts or solidifies in CO. , 

Aluminum solidifies in CO2 - 

Silver melts or solidifies in CO2 

Gold melts or solidiljes in CO2 

Copper melts or solidifies in CO2 

Lithium metasilicate melts in air 

Diopside, pure, melts in air 

Nickel melts or solidifies in H and N 

Cobalt melts or solidifies in H and N 

Palladium melts or solidifies in air 

Anorthite melts in air 

Platinum melts in air 



Deg. F. 



424.4 

582.5 

609.4 

786.7 

832.0 

1165.6 

1217.3 

1760.0 

1944.3 

1980.7 

2193.8 

2526.2 

2645.6 

2713.6 

2820.6 

2821.1 

3186.0 



Instruments for measuring temperature are classified by /. A. Moyer in 
Table 49, which also gives the temperature range and degree of accuracy 
usually obtainable. 



Table 49. Thermometers. 



Type 


Range Deg. F. 


Accuracy Deg. F, 


1. 


Mercury Thermometers. 








(a) Ordinary Type 


— 38 to + 575 


From 1.0 deg. in common 
instruments up to 0.01 deg. 




(b) Jena Glass, cap- 


— 38 to + 1000 


Higher ranges accurate to 




illary tube filled with 




1 deg. 




nitrogen. 








(c) Quartz Glass, 


— 37 to + 1500 


Higher ranges accurate to 




capillary tube filled 




1 deg. 




with nitrogen. 






2. 


Alcohol or Petrol-ether 


— 325 to + 100 


Accurate to 1 deg. 


3. 


Electrical Resistance 


— 400 to + 2200 


Accurate to 0.01 deg. for 
range of to 500 deg. 


4. 


Thermo-electric 


— 400 to + 3500 


Reliable to nearest 5 deg. 


b. 


Metallic-expansion, 
mechanical 


+ 300 to + 1000 


Uncertain 


6. 


Vapor 


+ 95 to + 1350 


Reliable to nearest 2 to 10 


7. 


Radiation 




deg. 




(a) Thermo-couple 


+ 300 to + 4000 


Reliable to about nearest 




in focus of mirror. 




20 deg. 




(b) Bolometer 


— 400 to temper- 


Reliable to about nearest 






ature of sun 


20 deg. 


8. 


Optical 


+ 1100 to temper- 


Reliable to about nearest 






ature of sun 


20 deg. 


9. 


Seger Cones 


+ 1100 to + 3600 


Reliable to about nearest 









20 deg. 



372 






o 
PQ 

i) 

G 
v 

X 

c 



o 



OS 



CO 
04 



CO 

X 
>> 

■i-> 

u 



HEAT 373 



Mercury Thermometers. Becniise of the uniform expansion of mercury, 
and its sensitiveness to heat, it is commonly used as the fluid for thermometric 
measurement within the ranges given in Table 49. Up -to temperatures of 
about 575°, the ordinary type of thermometer has a vacuum in the capillary 
tube above the mercury, while for higher temperature ranges the capillary 
tube is filled with nitrogen or carbonic acid gas under high pressure. Re- 
searches carried on at Jena have resulted in the production of a special glass 
for thermometers, known as the Jena normal glass ; this glass has practically 
the same coefficient of expansion as mercury, and hence is particularly suit- 
able for thermometers. 

Correction for Stem Exposure. Thermometers are usually graduated 
to read correctly for total immersion ; that is, with the bulb and stem at 
the same temperature. However, in general power plant measurement work 
it is seldom that the bulb and stem are at the same temperature: therefore, 
in order to obtain the correct temperature a "stem correction" must be 
applied. The stem correction (K) may be calculated from the formula: 

7^ = 0.000088 n (t—t) (36) 

in which ;; is the number of degrees of the scale reading not immersed, t^ 
the indicated temperature, and t the mean temperature of the air surrounding 
the stem as shown by a second thermometer. 

Calibration of a Thermometer. When a thermometer Is intended for 
exact work, its two fixed points, viz : the freezing point and boiling point, 
should be verified, and the graduations calibrated. To test for the accuracy 
of the graduations, a short column of the mercury in the stem, say 15 or 
20 degrees in length, is detached by jarring, and its length measured in suc- 
cessive positions through the entire length of the stem by means of the scale 
marked thereon. Where the capillary tube is relatively narrow, the thread 
of mercury will be correspondingly long, and thus b}^ its changes in length 
the irregularities in the thermometer tube can be determined and a calibra- 
tion curve deduced. 

Thermometer Wells. A thermometer well is used in measuring the 
temperature of steam or water when it is impossible to immerse the ther- 
mometer bulb directly. A well generally consists of a hollow plug, threaded 
at the upper end. It is screwed into a threaded hole in the top of the hori- 
zontal pipe through which the steam or water flows, the lower part of the 
well extending vertically into the interior of the pipe as far as the center. 
if practicable. The inside diameter of the well should be slightly larger 
than the outside diameter of the thermometer tube. The well should be 
filled with mercury or high grade mineral oil for temperatures below 500°, 
and with soft solder for higher temperatures. For superheated steam, the 
immersed portion of the well should preferably be fluted so as to increase 
the area of absorbing surface. 

Alcohol Thermometers. The low limit for mercury thermometers is 
about — 33 degrees Fahr. Hence, when it is necessary to measure lower tem- 
peratures, the alcohol thermometer is employed, in which alcohol or petrol 
ether is substituted for mercury as the expanding fluid. 

Electrical Resistance Thermometers are based on the variation of the 
electrical resistance of certain metals with the temperature. Platinum has a 
uniform resistance, and withstands high temperatures, hence is often used 
for this work. The resistance thermometer is made of a coil of pure annealed 
platinum wire wound upon a mica framework. The variation in resistance 
is measured by a Wheatstone bridge. Inasmuch as small currents are used 
with this device, delicate galvanometers are required. 

Thermo-electric Pyrometers, Fig. 185, are based upon the fact that when 
wires of two different metals are joined at one end and heated, an electro- 
motive force will be set up between the free or cold ends of the wires. The 
combination of two such wires is known as a thermo-couple. The voltage 



374 



HEAT 



so set up. when the '"hot" end is at a higher temperature than the "cold"' 
end, usually increases as the temperature difference increases and may be 
measured by a sensitive galvanometer or voltmeter. 




~P 



Fig. 185. Thermo-electric Pyrometer, 

There are two general types of thermo-couples, viz : high resistance 
and low resistance. The high resistance couple is formed of platinum and 
platinum-rhodium wires of small diameter and is often called a rare metal 
couple. Base metal or low resistance couples are made of iron versus con- 
stantan, chromel versus alumel and various other special patented alloys 
that are obtainable in sizes of Xo. 6 or 8 B. W. G. Platinum and platinum- 
rhodium couples ma}^ be used up to a temperature of 3500° F., while base 
metal couples are not suitable above 2000° F.. though their safe working 
temperature depends on the character of the alloys used. 

Thermo-couples, whether of the rare metal or base metal types, should 
preferably be housed in protecting tubes. Iron pipe will satisfactorily serve 
as a protecting tube up to 1500° F., but above this temperature, special alloy, 
quartz or porcelain tubes should be used. 

Mechanical Pyrometers, Fig. 186. depend for their action upon the dif- 
ferent rates of expansion of two different substances, that are generally in 
the form of iron and brass, or graphite and iron rods. The movement of 
the rods resulting from expansion is multiplied by gears and levers and com- 
municated to an indicating dial graduated in degrees. These pyrometers 
sometimes find application in the determination of boiler flue gas tempera- 
tures. They should be frequently calibrated, although at best they give 
unreliable results. 

A peculiarity of these mechanical pyrometers is apt to be disconcerting 
if the inexperienced observer is not warned. On placing in a flue, the outer 
element expands first and causes the pointer to indicate a very low tempera- 
ture, after which it rises to the proper temperature as the- inner element 
becomes heated. On withdrawing the instrument, the outer element cools 
first and causes the pointer to indicate a very high temperature until the 
inner element cools. Owing to this peculiarit}-. they are obviously unreliable 
where there are wide temperature fluctuations. 



HEAT 



375 




Fig, 186. Mechanical Pyrometer. 




Fig. 187. Recording Vapor Thermometer. 



376 




V 




x: 




■ij 




U-. 




O 




■M 




c 




C8 








a 




V 




X. 




■M 




+J 




CO 


, 


c 


>^ 


o 




'^ 


^ 




r/) 


u 




<D 


CS 





b 




d) 


<U 




v> 


-»-• 


u 


-M 


3 





u 


> 


r; 







U 


Pu 


u 

CO 


, 


<u 


K 


u 




(L) 
73 


Tt 


Ui 


Im 


"P 


O 


X 













o 
0. 



u 

.2 



HEAT 377 



Vapor Thermometers, Fig. 187, operate by the expansion of ether, mer- 
cury, or other liquids contined in a steel bulb and capillary tube, to which 
is connected a measuring or indicating device. When the bulb is heated, the 
vapor tension increases and operates the indicating or recording mechanism. 
The capillary tube of such a thermometer may be as much as 100 ft. long, 
hence these instruments are suitable for use when it is desired to have the 
recording device located on an instrument board at some distance from the 
point where the temperature is taken. This type of thermometer is used 
in the boiler room for the measurement of feed water and superheat 
temperatures. 

Radiation Pyrometers are instruments devised to measure temperature 
by means of radiation from incandescent bodies. In one type of radiation 
pyroEueter (Fery) the heat rays are focused by means of a series of mirrors 
upon the hot junction of a thermo-couple and the electromotive force so 
generated is indicated by a sensitive galvanometer graduated to read tem- 
perature directly. These instruments, if used correctly, will measure fairly 
accurately the temperature of fuel beds or furnaces, but their application in 
the boiler room has been limited. 

Optical Pyrometers are not used in boiler room practice, but serve 
rather to measure the temperature of small hot bodies. The Fery optical 
or absorption pyrometer measures temperature by focusing the heat rays 
by means of a series of mirrors and comparing the intensity of light emitted 
from the furnace with the light from a small comparison lamp. 

Seger Cones find little or no use in the boiler room, their use being 
restricted chiefly to the ceramic industries. Seger cones are small pyramids, 
consisting of various mixtures of quartz, feldspar, etc., and forming a scale 
with differences of 50 to 80 degrees F. between fusion or softening points. 
The cones are numbered in such a way that No. 1 melts at 2102 deg. F., No. 
022 melts at 1094 deg. F., and No. 42 melts at 3578 deg. F. To determine the 
temperature of a kiln or furnace, three or four consecutively numbered cones 
are placed upon a fire brick and introduced into the heated zone. The tem- 
perature indicated lies between the temperature of the cone, which still stands 
upright, and the temperature of the next one, which has begun to soften. 

Color as a Temperature Indicator. The color of many highly heated 
substances is an indication of the temperature. Results, however, obtained 
by this method are unsatisfactory, except for rough estimation, as the sus- 
ceptibility of the observer's eye and the surrounding illumination are sources 
of considerable error. Table 50 gives a schedule for judging temperatures 
in this way. 

Table 50. Pouillet Color Schedule. 



Appearance 



Incipient red 

Dull red 

Incipient red cherry. 

Red cherry 

Clear red cherry 

Deep orange 

Clear orange 

White orange 

Bright white ----- 

Dazzling white - 



Des 



980 
1290 
1470 
1650 
1830 







2010 




2190 




2370 




2450 




■/ 


2730 




2910 



378 HEAT 

Units of Heat Quantities 

' I 'HE British thermal unit (B.t.u.) is the amount of heat required to 
■■' raise a pound of water one degree Fahrenheit in temperature. It makes 
little practical difference at what part of the scale this one degree lies, but the 
*'mean B.t.u.," adopted as the standard, is Viso of the heat required to 
raise a pound of water from 2)2 to 212 deg., which is approximately equal to 
the heat required to raise it from 63 to 64 deg. 

The mechanical equivalent of heat is the amount of work that can be 
produced from or is convertible to a unit of heat. ]^lany scientists have con- 
ducted tests in which mechanical work was entirely converted into frictional 
heat; these tests have been checked b}' calculations, and it has been determined 
that 1 British thermal unit = 778 ft. -lb. of work. The more accurate value 
is 777. S2, at a point ( such as latitude 45 deg.) at which g, the acceleration 
of gravity, equals 32.174 ft. per second per second. 

The heat contained in a bod}' is a function of its mass, its temperature 
and its specilic heat, or heat capacity. The specific heat of a substance is the 
amount of heat required to raise a pound of it 1 deg. in temperature. The 
specific heat of water is therefore 1 B.t.u. at 63 deg. The specitic heats of 
all other substances express their capacity as compared with water. The 
greater the specilic heat of a substance, the more heat is required to increase 
its temperature through a given range, and the more heat it will give up 
when cooled. The specific heat of a solid body can be determined by heating 
it and immersing in water. The heat lost (as measured by the increase in 
temperature of the water) divided by its mass and its decrease in temper- 
ature, gives the specific heat. This is practically constant for solids, but 
varies slightly with temperature for liquids, and considerably in the case of 
gases. The calculation of the British thermal units involved in heating water 
-is therefore simple ; more extensive data are required to calculate the heat 
for vaporizing water, superheating steam, or that lost in flue gases. 

The specific heats of several common solid substances are given in Table 
51 b}' Lucke. 

Table 51. Specific Heats of Solids. 

Solid Specific Heat 



Amorphous carbon 0.1 170 

Cast copper _ 0.1138 

Brick work, masonry, stone 0.1298 

Coal 0.16 to 0.18 

Wood 0.45 to 0.65 

Glass - 0.2 to 0.241 

Cast Iron about 0.2 

Wrought Iron at 62 deg 0.0924 

Steel at Z2 deg 0.241 



A discussion on the specific heat of gases occurs later in this chapter. 

Heat Transfer 

A WARM body has a constant tendency to pass over its heat content to 
^*- a cooler one, and as their temperatures approach, the net rate of trans- 
mission decreases proportionately, until it reaches zero. Heat is transferred 
by three distinct processes : radiation, conduction, and convection. 

Radiation is the direct passage of heat energy in the form of rays through 
space or through a diathermanous medium. Solar heat travels by radiation, 
and is converted into sensible heat on striking the earth. Heat is radiated 



HEAT 379 



from the burning fuel and gases in a furnace, and the portion that strikes 
the boiler tubes aids materially in evaporation. 

Conduction is the passage of heat between substances in actual contact. 
In homogeneous bodies the heat transmitted varies directly as the area and 
temperature differences of the two surfaces under consideration, and in- 
versely as the thickness. Transfer rates can also be estimated or deter- 
mined experimentally for combinations of materials, such as metal coated 
with scale, or with grease and soot. All heat used in evaporating water 
in a boiler must necessarily pass by conduction through the clean or coated 
metal. 

Convection is the transfer of heat by the motion of the fluid containing 
ii. In traversing the heating surfaces of a boiler the hot gases give up heat 
by convection to the metal of the tubes from which it passes by convection to 
the water in circulation. 

Radiation 

RADIATION takes place constantly from all bodies, even though they 
may be cooler than their surroundings. The net gain or loss by radiation 
is the difference between the heat received and that emitted. The standard 
of comparison is the performance of an ideal "black body," one that would 
absorb all radiation incident upon it, and would radiate heat at the maximum 
rate. The British thermal units emitted by radiation from a "black body," 
per square foot per hour, by Stefan's formula equal 1600TV10^', when T is the 
absolute temperature of the body, in degrees Fahrenheit. With all real bodies 
receiving heat by radiation, a portion is reflected, and if the body is at all 
transparent to radiation, a portion is transmitted. The absorption factor, 
the ratio of the heat absorbed to that incident, is equal to the emission factor, 
which is the ratio of the emissivity (radiating ability) to that of a perfect 
black body. The emissivities given below are for use in Stefan's formula, 
the values being substituted for the 1600 used for a black body : 

Table 52. Radiation Constants. 



Eody 



Black body 

Rough cast iron, oxidized 

Dull wrought iron, oxidized. 

Lamp black 

Rough white lime plaster 

Water 

Polished wrought iron 

Clay, smooth 

Dull brass 

Slightly polished copper 



Constant 



1600 

1570 

1540 

1540 

1510 

1120 

467 

650 

362 

278 



The rougher a body is, and the darker it is when in the cold state, the 
higher is its radiative and absorptive power. 

The net heat transfer between two bodies depends upon their tempera- 
tures, on the character of their surfaces as affecting their emissivities, and 
on the angle of exposure. For two "black bodies" with parallel faces exposed 
to each other, the heat transfer is 

H = ^(T.'-T.') (37) 

H = Heat, B.t.u., per hour per sq. ft. 
Ti, Ta =:Temp. of hot and cold bodies, abs. deg. F. 




1725 H. P. Installation of Heine Boilers in the plant of the American 
Hard Rubber Co., College Point, Long Island, New York. 



HEAT 



381 



The temperature of a point exposed to radiation in a furnace setting 
can be determined by this law. Take for example a point so located on the 
side wall so that its angles of exposure to the fuel bed and to the boiler tubes 
are equal, the bed and tube temperatures being 2500 and 500 deg. respect- 
ively. As the point is at a uniform temperature and practically unaffected 
by the gas travel, the heat which it receives by radiation from the fuel bed 
will be equal to that which it emits to the tubes. Taking 1600, 1500 and 
1550 as the radiation constants of the fuel bed, firebrick and tubes respectively, 

ICF ^^^^ 10'^ - 10- 10- ^ ^ 

T = 2545 deg. abs. = 2085 deg. F. 

which is the temperature of the given point in the side wall, as influenced by 
radiation. 

Heat radiated to and from a surface in such a manner is often spoken 
of as "reflected," although the bulk of it is absorbed and then emitted. 

The total heat transmitted to the tubes depends upon the temperature of 
the fuel bed, and upon the area of the fuel bed exposed to the tubes, rather 
than upon the total tube surface. The glowing carbon radiates heat at a 
rate almost equal to that of an ideal black body, and while the tubes receive 
radiant heat from the walls and the flame, as well as from the fuel bed, the 
net transfer can be closely approximated by inserting the fuel bed and the 
tube temperatures and the area of the effective fuel bed surface, in the 
"black body" heat transfer equation. 

In a locomotive type furnace, the entire surface above and surrounding 
the fuel bed is heating surface, except the fire door, which covers only a 
small angle of the fire. The transfer by radiation is proportional, therefore, 
to the fuel bed area. In a furnace of this type having 40 sq. ft. of fuel bed 
at 2500 deg., the sheets being at 500 deg., the heat transferred by radiation 
would be 



1600x40 
10'-' 



I 2960^ — 960* i 



= 4,858,240 R.t.u. per hour. 



The height of the fire box v.ould not affect the total transfer by 
radiation, as the entire fuel bed is exposed to the cool heating surface. If 
the height was 4 ft., and the total sheet surface 200 sq. ft., the heat trans- 
ferred by radiation would be 24,291 B.t.u, per hour per square foot of 
heating surface. 

With an externally fired boiler, each portion of the hot fuel bed is ex- 
posed to hot walls as well as to the cold boiler tubes, and the walls are 
exposed to the fuel bed and the tubes. In each view of Fig. 188, the angle b 




Fig. 188. 



Application of Radiation Law to an Externally Fired Boiler, 



x^ 



HEAT 



represents the exposure of a point on the fuel bed to the heat-absorbing 
tubes, and a and c the angles exposed to surfaces at temperatures approxi- 
mating those of the fuel bed. By taking an average of b/lSG at a number 
of points in the fuel bed and the walls, a measure of the citcciii'c radiat- 
ing area of the hot surfaces can be ascertained. The right-hand member of 
the formula 2>7 (for heat transfer between two black bodies) can then 
be multiplied by this average, the result being the ai'crage net heat radiated 
by the hot surfaces to the boiler. 

The higher the fuel bed temperature the more heat passes to the boiler 
surface as radiant energ>- instead of being carried by the gases as sensible 
heat. Fig. 189 shows the extremely rapid increase at high temperatures, the 
radiation being four to five times as great at 3500 deg. as at 2500 deg. abso- 
lute. Each curve is plotted for a constant temperature (as indicated) of 
the soot coating on the water-heating plates. 



7000r 




l&OO 2000 2S00 3090 3500 _ 

Temperature of Fuel Bed and Furnace, Abs Deg F "" 

Fig. 189. Relation Between Furnace Temperature and Radiated Heat for 
Constant Temperatures ^800, 1200, etc.j of the Soot Coating. 

Tests by the University of Illinois on Heine boilers, with and without 
a baffle protecting the lower row of tubes, showed a much lower flue-gas 
temperature, and 3 to 5 per cent higher efficiency when the tubes were ex- 
posed to radiation. Little smoke was produced in this case, although if the 
amount of heat transferred by radiation is too great the tire is cooled, and 
combustion is incomplete. 

A fuel bed under the boiler gives greater transmission by radiation 
than does a Dutch oven. 

Up to the point where the products of combustion are cooled below the 
ignition temperature, any heat transmitted by radiation, instead of being 
carried by the gases, is clear gain. High transmission by radiation requires 
a large fuel surface exposed at a wide angle to the heating surfaces, and 
high temperature of the fuel bed surfaces. The latter, however, must not 
be so high as to damage the furnace lining or fuse the ash. 



li ]<: A T 



383 



Conduction 

CONDUCTION through a homogeneous solid is measured by the 
•f/-^lll-l\xr1n<T fr^rmnlo • 

C(h — td 



following formula 



// 



(3<S) 



// =:Amount of heat conducted = B.t.u, per sq. ft. per hour 
C = Coefficient of conductivity = B.t.u. per sq. ft. per hour per 
degree difference between the temperatures of two parallel plane 
surfaces 1 inch apart 
u = Distance between plane surfaces or thickness of substance 
/j, t-j, = Temperatures of the two plane surfaces 
Values of C for different materials are given below in Table S3: 

Table 53. Coefficients of Conductivity. 



Material 



Copper 

Aluminum 

Wrought iron 

Soft steel - 

Cast iron 

Hard steel 

Firebrick 

Water 

Glass (soda, window glass) 

Hydrogen 

Air 

Lamp black... 

Vacuum 



Conductivity C 



26381 
1428 



412 
322 


- at 212 deg. 


314 




180 




9.0 at 1300 deg. 


4.35 at 86 dcg. 


4.5 


0.976 at 60 deg. 


0.165 at 32 deg. 


0.215 at 212 deg 








The conductivity of solids varies slightly with temperature, iron de- 
creasing by 0.0229 for each degree Fahrenheit rise. With gases it varies 
as the "constant-volume" specific heat and the viscosity at different tem- 
peratures. 

That the metal offers only a small part of the resistance to heat flow is 
shown in boiler practice by actual rates of transmission. Consider, for 
instance, a boiler operating at the rate of 10 sq. ft. per equivalent boiler 
horsepower, corresponding to 3350 B.t.u. per sq. ft. per hour, with tubes 
Vio in. thick. The conductivity of iron at 400 deg. is 408, and substituting 
in the conduction formula, we get 



3350 



408 
0.1 



~(h — i,). 



t—t, = 0.82 dcg. Fahr. 

Higher rates of driving involve greater temperature differences, but the drop 
through the metal never approaches the drop between the gases and the 
water. Scale and soot coatings add considerably to the resistance, but even if 
the combination offers ten times the resistance of a clean tube, the temper- 
ature drop is only 8.2 deg. through solid material. This serves to emphasize 
the possibilities of working the surface at high rates. 




1000 H. P. Heine Standard Triple Drum Boiler, installed in the Walter Reed 

Hospital, Washington, D. C. 



HEAT 385 



In a test on a Hieine Boiler, the water surface of the >^-in. thick tubes 
was 41.5 deg. below the temperature of the gas surface. The heat conducted 
was, therefore, 

—^ X 41.5 = 136,000 B.t.u. per sq. ft. per hr, 

corresponding to 4.05 boiler horsepower per square foot, or 0.247 sq. ft. per 
boiler horsepower. 

Thermal resistance is the reciprocal of thermal conductivity, and the 
total resistance of several bodies through which the heat must pass, one after 
the other, is the sum of the individual resistances. A break in a substance 
creates a surface resistance, so that boiler seams in contact with the fire 
should be eliminated. 

Convection 

TN most boilers, the bulk of the heat is carried by the gases and by contact 
-^ with the heating surface delivered to the boiler. This process is called 
convection. 

While considerable work has been done to elucidate the subject of con- 
vection, it must be admitted that much research is still necessary, 

Rankine's convection formula is based on the assumption that the rate 
of heat transfer is dependent simply upon the square of the difference in the 
temperatures of the gases and of the heating surface, and is independent of 
the velocity of the gases. This assumption is now generally rejected. 

Many prominent scientists and engineers have made investigations that 
have provided interesting information. In 1874, Professor Osborne Reynolds 
formulated a law of heat transfer which may be expressed as : 

R = a+ b^y (39) 

where R ^ B.t,u, transferred per sq, ft. of heating surface per hour per 
degree difference between the temperatures of gas and metal 

W = Weight of gas per hour 

A = Area of gas passage 
a and b = Constants. 

This law is based fundamentally on the rate of flow of the gas over the 
heating surface ; it has been frequently and conclusively confirmed by Stanton, 
Nicolson, Jordan and others. 

Jordan summarized the convection law of heat transfer as follows : 

1. For a constant rate of mass-flow, the rate of heat transfer is pro- 
portional to the temperature difference between gas and metal. 

2. For a given temperature difference, the rate of heat transfer in- 
creases with increasing gas velocity according to a linear law. 

3. For a given gas velocity and a given temperature difference, the 
rate of heat transfer increases with the absolute value of the temperature. 

4. The rate of heat transfer depends upon the condition of the heating 
surface. 

5. The rate of heat transfer depends on the size of the channel through 
which the gas is flowing, the smaller the ratio of the area of the channel to 
the perimeter of the channel, that is, the smaller the hydraulic depth, the 
greater the ratio of heat transfer. 



386 HEAT 



The value of^a is influenced by the condition of the heating surface. It 
varies between 1.75 and 225. With reasonably clean surfaces, it is generally 
very close to 2.0, and this remains the case no matter what the circumstances 
may be. 

The value of b is of the most importance. It is influenced by the hydrau- 
lic depth of the channel, and by the temperature. All ordinarv conditions 
are met by writing b = 0.001. The effect of this, at say 2,000 and 4,000 
pounds of gas per sq. ft. of gas passage area per hour, is : 



/ 2.000 \ 

(™) 



2.0 + 0.001 I -^ — \^4=zR 

/ 4.000 \ 
and 2.0 + 0.001 I — ]=6 — R 



Some take a much higher value of b with a consequent!}- higher value of 
7? ; but as these higher values of R are not realized in practice when the 
radiation eftect is eliminated, it is customary to make an arbitrary addition 
to the amount of heating surface so deduced. 

Investigations now in progress by the Research Department of the 
Heine Cotnpany have yielded some surprising information. Under certain 
circumstances the value of b may be increased very considerably, — in some 
instances to as much as 0.004. To show the effect of this, the same gas 
rates as above are taken, namely. 2.000 and 4,000 pounds. 



/ 2.000 \ 



2.0 + 0.004 I ^ — \ = 10 = R 

/ 4.000 \ 
2.0 + 0.0O4 I — 1 = 18 = 7? 



The amount of heating surface required is, of course, inversely pro- 
portional to R when radiant heat is not considered. So that when \V/A = 
say 4.000 pounds, a boiler with i? = 18 would have a heating surface only 
one-third of that of a boiler with i? = 6, the capacity and efficiency being 
the same for both. 

Lawford H. Fry has made a broad investigation of the work of experi- 
menters in this line and has devised a formula which harmonizes the results 
of a large number of tests. This formula does not directly express the rate 
of heat transfer, but rather gives an expression for the rise or fall of tem- 
perature of a gas in its passage through a flue, the wall of which is at a 
higher or lower temperature than the gas. When the gas is hotter than 
the flue, 

lolog^^—lolog^^ =Mx (40) 

where .*" = Distance along the flue from entrance 
Ti = Initial gas temperature, deg. absolute 
Tz := Exit gas temperature, deg. absolute 
Tz =: Mean flue wall temperature, deg. absolute 
.V = Coefficient 
lolog = Logarithm of the logarithm 

Coefficient J./ depends on the flue dimensions and the rate of 
gas flow. 



HEAT 



387 



Fig. 190 is drawn from Fry's formula, and shows the relation of gas 
temperatures to proportion of heating surface passed over, with 2,500° initial 
and 450° exit temperatures in conjunction with a water temperature of 360°. 

The application of the law of high gas velocity to waste heat boilers 
has been mentioned in Chapter 4 on FURNACES AND SETTINGS. 



2600 
240O 
220O 
2000 

1800 

k 

" i600 

^ 1400 

I 

^|'200 
1000 
800 
60 
400 
200 









n 




























































































































































\ 






















































\ 






















































T 






















































I 






















































\ 






















































\ 






















































^ 












































































































\ 






















































\ 






















































> 
























































y 






















































\ 






















































^ 
























































y 






















































\ 
























































^ 






















































\ 






















































\ 
























































V 
































• 






















\ 






















































V 


^':t 










































































































\^ 






















































\r^ 




















































\ 


C-- 






















































V- 


\. — 




















































S 






















































^•=>>^ 






















































\, '- 






















































^.^ 


3 




















































s 


\h 






















































^ 


























































s. 
























































s. 


s, 














■ 










































v 


">, 
























































•^ 




























































>-^ 


























































"*■ 






























































->..^___ 
























































































































Tef 


VPf 


mtuh 


? f 


?/ 


,m 


w 


77 


'4 


f^ 


D 


r- 




a 




















i 

























































































































































































































































































































\Q 20 30 40 50 60 70 80 90 100 

Percentage of Heafing Surface Fassec^ 

Fig. 190. Relation Between Temperature of Gases and 
Heating Surface Passed Over. 




Three Heine Standard Boilers, in the American Express Co. Building, 
New York City, set over Detroit Stokers. 



HEAT 



38Q 



Temperature Drop in Boilers 

FIG 191 shows the results of tests by the Bureau of Mines on a Heine 
Boiler, operating at 4.4 lb. per square foot per hour, in which temperatures 
of both sides of the tube were taken. These tests also show the large tem- 
perature drop between hot gas and metal, and the small drop through the 
metal to the water; the temperatures at the l^^-hour point bemg as follows: 

Gases Gas-side Surface Wate^r-side Water 

At beginning of path 2552 400 358 347 

At end of plith - 688 352 349 347 




Fig. 191. Temperature Readings in Conductivity Test. 

The transfer of heat from metal to water, if the circulation is sufficient. 
is rapid, because of the high specific heat of water. The high rate of heat 
transfer m condensers, which may be more than 1000 B.t.u. per sq. fl. per 
hour per deg. difference, ilhistrates this. 



Combustion 

COMBUSTION is the process of oxidation or the chemical union of an 
element with oxygen, and takes place with such rapidity that considerable 
light and heat are produced. The principal combustible elements ni fuel are 
carbon, hydrogen and sulphur. 

The oxygen necessary for the combustion of fuel is provided by the air, 
which is a' mechanical mixture, not a chemical compound. Air consists 
principally of oxygen and nitrogen and contains small amounts of carbon- 



390 



HEAT 



dioxide, water vapor, argon and other rare and inert gases. These inert 
gases are ordinarily included with the nitrogen, so that the composition of 
air is generally given as : 





Per Cent by Volume 


PerC 


;ent by Weight 


0.. 


20.91 




23.15 


N, 


79.09 




76.85 



The chemical combination of oxygen with the combustible elements of 
fuels occurs in definite and invariable proportions — a law which may be 
better understood by the following brief references to elementary chemistry. 

All substances, whether gaseous, liquid, or solid, are either elements, 
compounds or mixtures. 

An element is a substance which cannot be reduced to a simpler form. 
Carbon, sulphur, oxygen, hydrogen, etc., are elements. 

A compound is a substance which can be reduced into simpler forms or 
elements by chemical process. Water, carbon-dioxide, iron sulphide, etc., 
are chemical compounds. 

A mechanical mixture contains one or more substances not held in 
chemical combination. Air, as mentioned above, is a mixture of the elements, 
oxygen and nitrogen, and the compounds carbon-dioxide, water vapor, etc. 

Molecules. If an element or compound be divided and redivided into 
particles, until the limit is eventually reached where the substance can not 
exist by itself without losing its characteristics, that particle is known as a 
molecule. If such a molecule be dissociated into its component elements, 
these elements are known as atoms. The elements are represented in 
chemical nomenclature by letters, such as H for hj^drogen, C for carbon, Fe 
for iron, etc., etc. Compounds are represented by groups of letters with 
subscripts which indicate the numbers and kinds of atoms contained in the 
molecule. For example, the symbol H2O for water indicates that two atoms 
of hydrogen and one atom of oxygen comprise one molecule of water. Atoms 
seldom exist uncombined, hence the symbols for oxygen, nitrogen, etc., are 
written O2 and No, which indicate that there are two atoms in the molecules. 
Carbon exists in a number of dififerent forms and hence there are many 
carbon molecules, each containing a different number of atoms. The latest 
investigations seem to indicate that the least number of atoms in any carbon 
molecule is twelve. 

Atomic Weights. The atoms of different elements have different relative 
masses or weights. As hydrogen is the lightest, its atomic weight is generally 
given as 1 and the weights of other atoms referred thereto, but sometimes 
oxygen is given as 16 and used as the basis. Table 54 gives the atomic 
weights of those elements most frequently met with in the combustion of fuels. 



Table 54. Atomic Weights. 



Element 



Hydrogen. 

Carbon 

Sulphur 

Oxygen 

Nitrogen... 



Symbol 



H 
C 

S 

o 

N 



Approx. 
Atomic Wts. 



1 

12 
32 
16 
14 



Accurate 
Atomic Wts. 



1.008 
12.005 
32.07 
16.00 
14.01 



HEAT 391 



Molecular J V eights. When two or more elements combine to form a 
compound, the relative weight of the molecule formed will equal the com- 
l)ined weight of the atoms which comprise it. For example, the water mole- 
cule. H2O consists of one atom of oxj-gen (atomic wt. 16), and two atoms 
of hydrogen (atomic wt. 1). 16 + 2=18, the molecular weight of water. 

Significance of Atomic and Molecular Weights. When expressing any- 
chemical reaction by an equation, the relative weights concerned in the re- 
action are obtained directly by using the atomic or molecular weights. For 
example : 

C + O, =^ CO. 

12 + 32 =44 

These relative weights may l)e expressed in kilograms, tons, pounds or 
in any other unit of weight. 

Where gases are Involved^ the relative number of molecules of the 
gaseous substance occurring in the reaction stand for the relative volume 
of that gas. Roman numerals are generall}^ used to designate these relative 
volumes, which may be expressed in cubic meters, cubic feet, etc. For 
example, in the combustion of methane, one volume of methane unites with 
two volumes of oxygen to form one volume of carbon-dioxide and two 
volumes of water vapor. 

I IT I II 

r/i4 + 20. =C0^ + 2H^0 

Heat of Combustion is usually expressed as the B.t.u. generated b}' the 
complete combustion of one pound of fuel. When elements or compounds 
enter into chemical combination with one another, heat Is either evolved or 
absorbed ; that is, the reaction Is either exothermal or endothermal. The 
reactions In combustion practice are exothermal. When one pound of pure 
carbon burns completely to carbon-dioxide, 14,544 B.t.u. are generated. 
When carbon Is not supplied with sufficient air for complete combustion, 
carbon monoxide Is formed and only 4,351 B.t.u. are liberated. The presence 
of even a small amount of carbon monoxide In boiler flue gases indicates a 
waste of fuel since each pound of carbon In this CO has yielded less than 
one-third of its available heat. The effect of the presence of carbon monoxide 
in the flue gases on boiler and furnace efflclencv Is explained In Chapter 15 on 
TESTING and Chapter 16 on OPERATION." 

Table 55 gives the weight and volumetric reactions and the heat evolved 
in the combustion of those elements or substances occurring in fuels. 

Ignition Temperature. As defined above, combustion Is characterized 
by the rapid chemical union of oxygen with the combustible substance. The 
rapidity or speed of the chemical reaction depends definiteh' on temperature. 
It is a well known fact that a lump of coal, even though surrounded by the 
requisite amount of oxygen for combustion, will not burn, imless it Is at a 
relatively high temperature. So also for every combustible substance there 
is a definite temperature below which the substance will not oxidize or burn. 
This temperature, which is known as the ignition temperature, is given in 
Table 56 for various components of coal and for CO. 

It is to be noted that the fixed carbon In coal ignites at a lower tempera- 
ture than the volatile hydrocarbons. Carbon monoxide will Ignite at about 
1210 degrees F. Therefore, with poor firing, delayed or secondary combustion 
may take place If oxygen is mixed with the CO In the proper proportions at 
a temperature of 1210° or above. 



392 




HEAT 



393 



_3 



A 



Q 

c 
o 



3 

a 

o 
U 



in I 

in I 



Si 
CO 
H 



IT) 





^^-^^ 


--V.-V 














^ (N 


ro T*H 














v_^^_^ 


^^ — '^ — ' 












-* 


ro Oi 


\0 (M 


o 


o 


lo 


O 


O 


Th 


ON CO 


rs On 


o 


rt< 


u^ 


o 


fN 


lO 


■^ CO 


O 00 


o 


ON 


lO 


o 


»o 


















-* 


O Ti< 


O-H 


Tj^ 


lO 


••— 1 




d" 




•«—( 


vOiO 






r<i 


r^ 


CN 






< 






3 C o 

S 6 g 
oiJ o 
OHO 






o 
+ 

u 



u 
II 

o 
+ 



o 

u 



o 
+ 



c 


c 


o 


o 


-Q 


^ 


u 


Ui 


C3 


rt 


U 


u 



o 

u 



o 
+ 

o 

u 



^ PC 



^ o 
+ 



cn 
II 

O 
+ 



o 

cn 



o 

+ 







o 


o 


a PC 


<M 


CN 


+ 


+ 




Oi 


. o 


^o 


^u 


u 


^ 


II 


II 



X 

CN 

+ 

o 

u 



o 
>x 

4- 



+ I + 



O ! tl 



X 
u 






^ I s o 

X i '-' " 















o 


o 












o 


<N 

X 












CO 


£ 


CN 


CN 




6 


o 




o 


CN 


+ 


+ 


o 

u 


K 


o 


CN 


+ 


d 


d 


CN 

11 

9 


(M 


c/^ 


11 


o 


u 


u 


11 

o 

+ 


11 

6 


'L 

o 


d 

CD 


u 
II 


11 


CN 

II 


+ 


+ 


+ 


+ 


o 


o 


o • 


o 


IN 


■•Si 


C/1 


CO 


lO 


CO 


^ 


u 


:i: 




r-i 


+ 


+ 


+ 




CN 


CN 






re 


X 

u 

CN 


X \ 

U 1 



rsi 


00 


CN 


^ 


■* 


o 


o 


] 

00 




CN 




o 


o 




(N 


CN 

i 



o 


o 

u 


£ 


J{ 


J) 


X 

u 


X 














u 


u 



o 

c 
o 



o 

u 



C 
o; 
be 
O 
u 

X 



a. 
cn 






c 



c 



vO 

+ 

O 

u 



o 

t 

X 



u 



c 

03 






§o5E 

^""" P in 
>- *- ^ — 
0) 0) o o 



394 HEAT 

Table 56. Ignition Temperatures. 



Combustible Ignition 

Substance Temperature Deg. F. 



Fixed Carbon — Bituminous Coal _ 766 

Fixed Carbon — Anthracite Coal — .. 925 

Carbon Monoxide .._ 1210 

Hvdrocarbon? 900-1200 

Hvdrogen - 1130 

Sulphur --. 470 



Theoretical Furnace Temperatures may be calculated on tlie basis of the 
following formula : 

where t = Temperature of combustion 
/, = Temperature of air 
r{ =^ B.t.u. developed b}' combustion 
rr' = Weight of products of combustion 
l' =: Mean specific heat of products of combustion between fi and t. 

The use of this formula involves a trial and error method in the deter- 
mination of the mean specific heat of the products of combustion. The 
theoretical furnace temperatures calculated by the above formula or modifi- 
cations of it have but little value to the engineer, as the actual furnace tem- 
perature is affected by variations in the rate of air supply, by the complete- 
ness of combustion, and by radiation from the fuel bed and flame to the 
cold surrounding surfaces. Actual furnace temperature will therefore always 
be lower than theoretical temperatures. 

Air Theoretically Required for Combustion. Table 55 gives the combus- 
tion reactions which occur in the burning of fuel. From these, the amount 
of ox3"gen necessar\" and consequently the weight of air theoreticalh* re- 
quired can be readily calculated by means of tlie atomic weights of the 
substances involved. 

The method of computing the air required for the combustion of carbon 
to CO2 will be given in the following example, which is tj-pical of the manner 
in which the results given in Table 57 are calculated. 

From Table 55 it is obser\-ed that one atom of carbon unites with two 
atoms of oxygen to form carbon dioxide. 

C 4- O, = CO... 

From Table 54 it is noted that the atomic weight of carbon i*; 12 and of 
oxvsren is 16. hence 

12 4- (2x16) =44. 

or twelve parts of carbon by weight unite with thirty-two part? of oxygen 
by weight to form fort}-four parts of carbon dioxide b}- weight. Xow, if 
we consider one pound of carbon as being burned, the weight of ox>gen 
necessar\^ for combustion will be ^/^ or 2.667 lbs. 

Since air contains 23.15 per cent oxAgen by weight, there will be re- 
quired 4.32 lbs. of air to supply 1 lb. of oxygen. Then, 

2.667 V 4.32 = 11.52 lbs. air required. 



HEAT 



395 



Table 57. Theoretical Air Requirements per lb. of Combustible. 



Combustible element or 
Compound 



Oxygen 

Required 

Pounds 



Air 

Required 

Pounds 



Air 

Required 

cu. ft. at 80° F 



Carbon to CO 

Carbon to CO.. 

CO to CO, 

Hydrogen 

Sulphur to SO.,... 
Sulphur to SOa... 



1.33 
2.67 
0.57 



5.76 

11.52 

2.47 



78.4 

156.5 

33.5 



8.00 
1.00 
1.50 



34.56 
4.32 
6.48 



469.5 

58.6 
88.2 



Methane 4.00 

Acetylene 3.08 


17.28 
13.29 


234.8 
180.9 


Ethylene 1 3.43 


14.81 201.6 


Ethane 3 73 


16.13 
6.10 


219.5 


Hydrogen Sulphide ' 1.41 


83.0 



The theoretical air requirements given in Table 58 are calculated on the 
basis of the approximate atomic weights. The Bureau of Mines gives the 
following formula for calculating theoretical air requirements, based upon 
the accurate atomic weights. 

[F r= 0.1158 C + 0.3448// — 0.04336 {OS) (41a) 

where : W = \h. of air per lb. of fuel 

C = Percentage of carbon, ultimate analysis 
H = Percentage of hydrogen, ultimate analysis 
^ Percentage of oxygen, ultimate analysis 
S = Percentage of sulphur, ultimate analysis 

The weight of air will be per pound of coal, per pound of dr}- coal, or 
per pound of combustible, according to the basis on which the analysis is 
reported. 

Air requirements of typical coals were calculated by the Bureau of Mines 
formula as follows : 







Table 58. 


Air Required per lb. of Coal. 








COAL 




B.t.u. 
per lb. 


Coal by Analysis, Per cent 


Pounds 

Air per 
lb. of fuel 


Air per 
10,000 




C 


H 


S 


B.t.u., Lb. 



Lignite, poor. 

Lignite, good 

Sub. bit., poor 

Sub. bit., good 

Bituminous, poor 

Bituminous, good 

Semi-bituminous, poor 
Semi-bituminous, good 
Semi-anthracite 

Anthracite, poor.. . . . . 

Anthracite, good 



10,560 
10,960 
14,130 



14,120| 
14,700 
13,700| 



60.1 
60.1 

78.0 

80.7 
84.6 
80.3 



5.9 
5.4 
5.3 



27.0 
17.9 
11.5 



0.6 
4.9 
0.6 



4.6 
4.8 
3.6 



4.6 
5.1 
3.6 



1.0 
0.5 

1.7 



8.2 
10.3 



10.7 
11.2 
10.4 



6,350 


37.5 


7.1 


45.6 


1.0 


4.8 


7,190 


41.3 


6.8 


40.8 


0.9 


5.4 


9,210 


52.5 


6.1 


34.1 


0.3 


6.7 



7.52 
7.38 



7.30 
7.49 
7.29 



7.60 
7.64 
7.62 



12,5801 
13,350' 



79.2 
81.4 



2.2 
3.1 


4.6 
5.1 


0.5 
0.6 


9.7 
10.2 



7.74 
7 . 65 



396 




n 




(U 


V) 


C 


u 




V 


(L) 


+J 


X 


CC 


Lw 


^ 


o 


V 




a 


Oi 


3 




in 


ffi 


V 




c 


o 


4) 


o 


ffi 


lO 






'0 


00 


c 


G 


CC 






c 


CO 


CC 


l-l 


■iJ 




c 
o 
o 


o 


- 


IL) 





c 


u 


OJ 


c 


ffi 


(U 


«+-. 


o 


o 


o 




^ 


cu 


CC 


X 


() 






o 




O 


b 


1— ( 


< 


(N 


(U 


0) 


4J 


CC 


(«-< 


Wi 


o 


<u 




iX 


7 





CO 






>> 


^ 


ii 

CC 




a 


(U 


fi 


u 

(U 


o 
U 


Ih 




^ 


CO 


CC j: 


JH 



< 



HEAT 397 



Table 58 shows that while the weight of air required per pound of fuel 
varies greatly with the composition of the coal, it is nearly proportional 
to the heat value. The weight may run from 7 to 12 lb. per pound of coal, 
and averages about 7.5 lb. per 10,000 B.t.u. 

Air Actually Required for Combustion 

IN practice it is necessary to supply more air than that theoretically re- 
quired, owing to the products of combustion getting in the way 
when combustion is nearly complete. At the beginning of combustion in a 
theoretically perfect mixture of CO and air, CO and Os molecules will come 
together more frequently than when they are impeded by CO2 molecules 
formed as combustion progresses. The last free molecules of CO and O2 will 
probably not come together until the temperature has fallen below their 
combining or ignition point. Combustion, therefore, is always more intense 
in the earlier part of a flame and is languid at the tip. Mixing, agitation, 
or eddying of the gases will hasten combustion, but an excess of the O2 mole- 
cules is still necessary to ensure complete combustion in a reasonable time ; 
the more thoroughly the air is distributed and mixed with the combustible 
gases, the less excess will be required. Even in gas-burning installations, 
where the air is intimately mixed with the fuel, some excess air must be 
used, and appreciable time is required to complete combustion. This is 
shown by the CO present in the flue gases, if the comparatively cool heating 
surface is too close to the burner so that the flame reaches it and its tip 
is extinguished. The combustion space between the fire and the heating 
surface should, therefore, be ample, and should be so arranged that the gas 
stream is diverted and broken up. In coal burning furnaces an excess of 
at least 40 per cent, or 1.4 times the amount of air theoretically required, is 
usually necessary. 

Products of complete combustion of fuels containing only carbon and 
hydrogen are carbon dioxide and water, as will be noted by reference to the 
reaction equation given in Table 55. The weights of these products may be 
readily calculated by the use of atomic weights, and the relative volumes will 
be noted in the volumetric equations in Table 55. 

The volume of CO2 resulting from the complete combustion of carbon 
is the same as that of the oxygen consumed, because each molecule of 
oxygen, O2, takes up an atom of carbon to form a molecule of CO2. 
Therefore, the CO2 and the unused oxygen in the flue gases cannot possibly 
exceed the 20.9 per cent of the oxygen in the atmosphere. But the volume of 
CO resulting from incomplete combustion is twice that of the oxj'gen con- 
sumed, because each atom of the oxygen molecule takes up an atom of carbon 
to form a CO molecule, thus making two molecules of CO for each molecule 
of O2. Therefore, if CO is present, the (CO2 + O2 + CO) in the flue 
gases can exceed 20.9 per cent. The steam which results from burning the 
hydrogen in the fuel condenses and does not show in the analysis, conse- 
quently the oxygen consumed disappears, and the highest possible propor- 
tion of CO2 and O2 in the flue gases is less than 20.9, — being about 19 per 
cent with bituminous coals. 

The analvsis of the products of combustion is discussed in Chapter 15 
on TESTING. 

Combustion Losses. In the combustion of fuel, certain losses occur which 
vitally affect boiler efficiency. These losses are (1) the loss due to the in- 
complete combustion of carbon, (2) the loss due to latent heat of moisture 
formed in the burning of hydrogen, (3) the loss due to unconsumed carbon 
in the refuse, and (4) the loss due to incomplete combustion of the volatile 
hydrocarbons. The determination of these losses, together with certain other 
losses, inherent in methods of boiler operation, such as heat carried away 
by chimney gases, heat lost by radiation, etc., is discussed under the subject 
of the heat balance in Chapter 15 on TESTING. 



398 



HEAT 



Properties of Gases 

I 'HE general law for the effects of temperature and pressure on gases is 
-*- represented by the following equation : 



I'P = RT 



(.42) 



V = \'olume. cu. ft. per lb. 

P = Pressure, lb. per sq. in. absolute = gage pressure -|- 14.696 

R =: Constant, differing with the gas 

T ^ Temperature absolute =:: deg. Fahr. -}- 460. 

Equation 42 shows that the volume increases with rise in temperature and 
decreases with rise in pressure. With pressure unchanged, at temperature t. 
the volume is 

VJt,-\-460) 
fi4-460 

For constant temperaiure, at Po the volume = ViPJPa, where P^ and 
P, can be expressed in pounds per square inch absolute, or in inches or 
millimeters of mercury. 

When the desired value is to be derived from the volume under 'standard 
conditions." ['i is the volume at 32 deg. and atmospheric pressure, which 
corresponds to 492 deg. absolute and 14.696 lb. per sq. in. pressure (760 mm. 
or 29.921 in. of mercury). 



Table 59. Physical Characteristics of Gases Involved in Furnace Work 



At 32 " F. and atmospheric 
pressure 




— =:lb. per 
V cu. ft. 



At 80 " F . 
Lb. per cu. ft. 



Hvdrogen, Ho 5.3140 

^lethane, CH, , 0.6682 

Carbon Monoxide, CO! 0.3826 


177.900 
22.372 
12.809 


0.00562 
0.04470 
0.07807 


0.00512 
0.04083 
0.07113 


Nitrogen, X2 0. 3824 , 12. 801 

Air 0.3701 ' 12.390 

Average flue gas 0.3555 11. 920 


0.07812 
08071 
0.08400 


0.07127 
0.07353 
0.07650 


Oxvgen, O2 0.3348 

Carbon Dioxide. CO. . . 2420 
Sulphur Dioxide. SO-.. 0.1635 


11.208 

s.ias 

5 . 473 


0.08922 
0.12341 
0.18271 


0.08129 
0.11244 
0.16646 



The densit}', which is the reciprocal of the volume, decreases with rise 
in temperature and increases with higher pressure. 

The changes in volume and density of the gases referred to in Table 59 
are shown in Fig. 192. 

Air containing the maximum amount of vapor for the existing tem- 
perature is said to be "saturated." Fig. 193 shows the weight of pure dry 
air for temperatures from to 212 deg. at standard atmospheric pressure 
04.696 lb. per sq. in.), also the weight of air and vapor in a saturated 
mixture under the same pressure. 



HEAT 



399 



0.20 



,0.15 



bo.io 



'l>, 



0.05 



0.00 



80 



eo 



40 



I 20 



, ..,,,.,. _ 


I 


\ 


\ 


V 


\ 


' \ 


\ \ 


\ \ 


' \ 




' N^ i\ ^v 


>^V^ \ '"sj^ 


^S^ "^^ ^^ ^«v 


^'^^^v^^^ "^^"^ 


\ -^-^ ^ ^^t '^ ?• •«. ^ ' ^ 


'^^i^ ^v^ ^^ ■'^ ^ ^ ^ "~" ' """""■"■ — 


r""~T--+-.ZT^'*'™*=^SSE:~II^ 


Hydroqen(H2) =-Z^"" 


, L -1 1 1 1 1 1 1 1 — 1 1 1 1 1 1 1 1 1.. 1 1 


/ 


/ ^^ 


/ r ^^^-^ 


/ if^^V^ 




rW (^^i<#^'^/''fO^'' 


"M 'fW^^'^^W 


csV A^^jk'%^ ^^' 


W i^^'^ ^^ 


\/ ^ ^^^^fiC^' ^'^ 


/ (^'!^'^^^'th -^'" 


/ /,a«^^^.rt(?«a,[cOii^' 


/ ..<^.^'^^'W4^\,.Q^ ^^^ 


/ „oi^^''VbomTnL,-^«i^^" 


> C^^^ ^f^UMrfY 




^'0' ^^ .---^ 


^^L^'l^ — " 


i--'^ 





-4(00 500 iOOO 1500 2000 2500 

Degrees Fahrenheit 

Fig. 192, Temperature in Relation to Volume and Density of Gases. 



Table 60 gives the weight and volume of air at temperatures to 1000 deg., 
and pressures up to 100 lb. gage. Intervening values can be interpolated by 
the use of the general laws explained above. 

Specific Heat of Gases. There is frequent necessity for the use of the 
specific heat of gases in the computation of combustion data. As defined in 
the units of measurements used in power plant work, the specific heat of a 
substance is the B.t.u. required to raise tlie temperature of one pound one 
degree. The specific heats of all substances, whether gaseous, liquid, or solid, 
vary with temperature. In the case of liquids or solids, there is little differ- 
ence between the specific heats at constant pressure and those at constant 
volume. However, for gases there is considerable difference in the specific 
heats under these two conditions. The gases in combustion practice may be 
assumed to be at constant pressure. 

Specific heats may be still further classified as being instantaneous or 
mean. The instantaneous specific heat of a substance is defined as the amount 
of heat required at a definite temperature to raise the temperature of a 
unit weight 1 degree. The mean specific heat of a substance for a given 
temperature interval, is the specific heat l)y whicli tlie temperature dift'erence 
nmst be multiplied to determine the amount of heat necessary to raise a imit 
weight through the given temperature interval. The mean specific heat is 
generally used in the calculation of combustion data. 



400 



KEAT 



Table 60. Weight and Volume of Pure Air at Different Pressures- 



^ 






Gase pr€ss-.ir6S 


25 ill lira. re'i- 






E. — 


O-Ib. 


5-Ib. 


KMb. 


2D4b- 


504b. 


KMMbL 


f- ~ 


W V 


W T 


W T 


W V 


W T 


W T 



:: :^^^ ^- ::^ ^ : soo' 3.6:: ": 1.49 

SI I4i:.5 7.0i:.i9^5 -5. 01 .5720^ 3.6f .do8 1.50 
9q\ . 1395 7.16. 19551 5 . 12 . 3645 2 . 75 . 645 1 . 55 



30 
32 
40 



.0811 
.0S09 
0795 



12.34 
12.38 
12.59 



1366 
1360 

13:3S 



7.3c 
7.47 



18761 



50 
60 
70 



078012.84 
076413.10 
075013.35 




7.6i 
7.79 

7.94 



1839 
1803 

1770 



5.44:1.34321 2.92L6 ' 
5.55 .3362 2.98^.5; 
5.65 .3302 3.03 .5S4 



I ^ 



71 



80 

90 

100 



0736113.60 
072313.83 
071014.10 



.0988110.13 
.097010.32 



.0954 



10.50 



1239 
1218 
119 



8. OS 
8.21 
8.36 



17381 
1707 
1676 



D. to 

5.86 
5.97 



.3242 
.3182 
3122 



3.09 
3.14 
3.21 



.5*2 
561 
.551 



1.75 
1.78 
1.83 



110 
IPO 
130 



.0698114.35 
.068614.58 
.0674 



0937 

0921 

14.861.0905 



10.69 
10.87 
11.07 



1176 
1155 
1135 



8.51 
8.66 
8.82 



1615 
1618 
1590 



6.08 
6.18 
6.29 



.3070 
.3018 
.2966 



3.26 
3.32 
3-38 



.512 
.533 
.524 



1.85 
1.88 
1.91 



140 
150 
160 



.0663115.09 

.0652 15.36 
.064215.601 



.0889 
.0874 
.0669 



11.27 
11.47 
11.53 



1115 
1096 
1078 



8.97 
9.13 
9.281 



1565 
1541 
1517 



6.39 
6.49 
6.60 



.2915 
.2865 
.2820 



3.43[.516 
3.49-508 
3.55-499 



1.94 
1.97 
2.01 



170 
180 
190 



.063] 
.0622 
.0612 



15.86 
16.10 
16.3 



0846111.831 

0833^ 

0820 



n-" 



10621 



9.431 

o '*?' 



.1493) 



6.691 



.2775 

2"30 

-:?0 



3-61 
3.67 



-491 
.484 
.476 



2.t"i4 
2.07 
2.10 



200 
SO 

240 



.0603 
0585 



a5681 



16.60 
17.12 
-62 



.080 
.07S: 

.0700 



'.-^,\ I .021. 
:3S:3' 7.24 . 



2ooo 
2675 
2605 



3.77 
3.81 
3.85 



.470 
.457 
.444 



2.13 
2.19 

2.20 



260 
280 
300 



118- 101 
18.61 
19.13 



,07^ 
.07i:i 
. 07K 



:^ ii.os 



130. 
1273 
1237 



7.62 
7.85 
8.09 



.2435 
.2370 
.2300 



4.11 
4.22 
4.35 



-431 
-420 
-407 



2-32 
2.38 

2.45 



350 
400 
450 



.04911 
.0463121.65! 

.043: 



8.62 
9.18 

■?.68 



.2160 
.2035 
.1925 



4.64 
4.92 
5.20 



.382 
.360 
.340 



2.62 
2-78 
2.95 



500 

550 
600 



.0il4 
039^ 
0370 



^ :j.23| 
oOiiO.76 

-n' 11.31 



1820 
1730 
1650 



5.50 
5.78 
6.06 



.322 
.306 

-292 



3.11 
3.27 
3.4^3 



700 
800 
900 



aM2 
0316 
0293 



29-25 
31.70 
.34.18 



0460t21 . 75 
.042^: - 
039 - 



oo 



m 



1509 
1390 
1287 



6.64 
7-20 
7.76 



267 
.246 
.227 



4.06 
4-41 



1000 1.0273 



36.68 



.036 - 



^ :5.56[.1199 8.34 .212 



4.72 



Yaliaes in above table based upon pare air a: a:- -zi^.: : -^^jrre (14.69€ lb. per sq. in- 
or 29.92 in. vaescarj). 

w=Weig|it in pounds per cubic foot. T=l/w=Valiiine in cobic feet per poond. 

There is considerable disagreement between the specific heats of gases as 
determined bv many investigators. Prof. G. B. Upton collaborated the work 
of Mallard, LeChatelicr, Holbom and Henning, Langen, Pier and others, and 
derived the formulas of Table 61, which are sufficiently accurate for engineer- 
ing calculations. 



0.09 


















HEAT 


















4 


























/ 












































/ 




















^ 


^.^ 






















/ 






















TV5; 


fe^ 




















f 


















0.08 






^< 


=5^ 








































^ 










































^ 


fe^ 










































^ 


^ 


-«^ 






raj. 


































"^ 


c>^ 


^*«N», 






















0.07 
















•v 


^"^^ 




l/t-^ ■ 


































"S 






^«r<7/>/^^ 


































^ 




-r^""H-^c^^/;-/i._. 
































X. 




>^ 


/^^yi: — ki^'r^^^//?!. . 






v> 
























SsTv 


^^^;,^p- 


=^-T-^ 


'A 




cUUb 


























<t-^ 


"^^47- 






■■^==* 


— *: 


Z) 






















i 




> 


<^ 


^ .£y^ 


<^^^ 






























/ 






\rr<^ r^/i?">;r 


L^o 






























/ 








^1. -v^.-^ 


S^-^^. 






o0.05 






















/ 








V-^ 1 ^> 


^ 


■Q-^ 


























/ 








^ 






^f^. 




rs 






















/ 










^ 




> 


<^ 




:? 




















--S- 


1- 










A^ 


L*5>o 






^ 


^^- 


° 004 
















' 




^v) 














\V" 






N: 




















.<L7 














\^ 






\ 




















't/ 
















v^ 






) 




















-v^/- 
















v^ 




-^ 


-2 0.03 












' 






T^^; 


h- 
















-\<i^ 




^ 


















f\/ 




















^"^ 


/ 




-C 
















iV 




















Vv/ 




















A'/ 




















C \* 


c 




^ 
















':f. 


/ 


















(^ 


K 


_Cs>_ 




=="0.02 
















AV 


































Cyvr- 


















^ 


(Vv^ 


Vo 


\ 


















\^ 


l/ 


















^^1 


\^ ' 


\ 


















^^V 


















■r^ 


C^£ 




\ 
















J•^^'^ 


















\\fy 






> 




0.01 










irits 


(^r^ 


/■ 
















Mi>i>^ 








\ 










■y 














I. if 


cn^^^-<i+u^ ' 










\ 










..oei^ 










Ticf. 




TfS2ii::-^^. 


JW' 










\ 






fcffef 


-1/af^'^ 




nlFT 




•^ If-t^fl 


■)0j\ 


(J^^rz 


,01^ 














\ 




_y 


a 


pi4 


& 


P^ 




<3 


lie 














> 



401 



i 100 

Tempera+ure, Degrees. Fahrenheit 

Fig. 193. Weights of Air or Water Vapor. 



200 212 



Table 61. Mean Specific Heat Formulas (Const. Press.) 

Range o° C to f° C 



Gas 


Formula 


0. 


0.216 4- 0.000014^ 


A^ and CO 


0.243 + 0.000019/ 


CO, 


0.200 + 75 X 10-"/— 21 X 10-«/- + 2.2 X lO-^^^^ 


H, 


3.369 4- 0.00055/' 


Air 


0.237 + 0.00O019f 


Water Vapor 


0.452 + 7.4 X 10-"/ + 92.6 X 10-»/2_ 20.6 X 10-^2/3 



The curves, Figs. 194, 195 and 196, showing the mean specific heats at 
constant pressure of those gases most commonly met with in combustion 
practice, are based upon the formulas given in Table 61. Above a tempera- 
ture of about 2000° F., the values are somewhat uncertain and the results are 
dependable only to the first two significant figures after the decimal point. 



HEAT 



403 



\ 


-r 
\ 






-\- 














1- 




































■■ 






] 






























































\ 


\ 




\ 














l 










































\ 


\ 






\ 












\ 












































\ 


\ 






1 












\ 














































\ 






\ 












\ 














































\ 


\ 




\ 


























































\ 


\ 




\ 














I 














































\\ 


















\ 














































* 






V 












\ 
















































[ 




\ 












\ 
















































\ 




V 












' 
















































1 






^_ 












1 














































\ 






\ 












\ 














































] 


\ 




\ 












\ 
















































\\ 




\ 












\ 
















































'\ 
















1 
















































h 




\ 
1 














1 














































\ 


\ 


\ 














\ 














































\ 


\ 


\ 














I 


















































\ 


r 












\ 
















































\ 


\ 


r 

4. 












1 
















































^ 


i 


T 




























































\ 

1 


1 


n 














I 
















































I 


^\ 














\ 
















































\ 


>\ 














\ 
















































\ 


^i 














1 
















































1 


^ 














I 


















































^ 






























































i 


V. 














\ 
















































pi 


\\ 














\ 
















































: h 














' 
















































. \ 


^ 




























































r 


>V v.\ 


\ 












1 
















































T 




\ 












\ 


















































■"' "<.■ , 


N, 












\ 




















































\ 












' 


















































^v ^ 




^ 




























































,^' 




>, 




























































^L 


i 


N 


\ 








t 


\ 
















































^V 


\ 


-c 


\ 








^ 


A 


















































\ 




^ 


< 








a 


















































^ 






^ 








M 
















































. ,0)1 


i 








\ 




\ 


^i 


















































\ 






< 


£>^ 


k 




\ 
















































^ 


J 








^N 


L_ 


\ 
















































^-T 












r-N 1 


















































'^\ 


I 












s 


















































1 


[ \ 












V 




















































^ 












^ 


V 1 


















































-^ lT 












^v\ 


















































\ 














SJ 


















































\ 














s 






























































\ 


































































\ 














































\ 
















\ 




S, 












































\ 




\ 


















Sj 










































\ 




1 


















s, 












































i 




















V. 






































\ 




\ 






















> 


s. 




































\ 




1 
























> 


s 


































^ 






























> 


^. 






































\ 


























> 


^, 
























L_ 






































\ 




. 















a. 



c 
o 
U 



k 



% (L) 

Qj O 



^^ 






^ 


CJ 


«M 


(U 




a 




CO 


^ 


c 

CO 


^ 


^ 


<i 


rj-' 


C> 


(^ 


<J0 


I— 1 




bb 






5i 


[I. 


Ci 




vo 





00 


s. 


U» 


in 


<**■ 


ro 


CSI 


«„ 


O 


r>* 


CM 


CM 


Cvj 


eg 


04 


Cvj 


CM 


oa 



(h 



4if9fi o/^/09ds 



404 



HEAT 




-^^^H ^.'J-'.^^^S 



HEAT 



405 





\ 


^ 


\ 


^ 


\ 


>s 


\ 


^ 


^ 


:s 


^ 




^ 


N 


^ 


V 


V 




V 


r 


^ 


\ 


\ 


\ 


V 




5^ 


-^ i ^ 


^v 


t^ 


l<^ 


<a.\ 


">> 


v\ 




^\ 


i ^T 


. ^. 1 


\ 


V 


^ 


V 


^ 


_ „ r 


3 


T" 


5 


i 


Y 


1 


r 


V 


j 


L 


V 


\ 






L 








I "f 



CI* 



CVJ 




c 


<Vi 




CO 

c 


^ 




o 


^ 




U 


«\i 




4-> 
CO 


^ 


k 


O 


on 


^i 


a 




J' 


CO 

> 


Q>) 


-$ 


u 
i) 


V>) 


S'^ 


4-1 


^ 


Jk 


CO 




5^ 


^ 




^ 


<+4 


^ 


k^ 


o 


^ 




■M 






CO 

X 


v:> 






Jji 




U 


iVj 




(U 

a 


^ 




CO 


Si 




^ 









o 


o 


o 


o 


O 


o 


o 


o 


o 


o 


o 


o 


00 


"^ 


CM 


o 


oo 


CO 


^ 


«M 


o 


oo 


vo 


"^ 


UJ 


to 


«4) 


K> 


m 


"0 


in 


»o 


»f) 


^ 


''^ 


^ 



/^// ^VP^'^S 



406 







<v 




^ 




o 




■M 




CO 




-d 




OJ 




q> 




(4-1 




Ui 




(U 




T3 




C 


, 


^>. 


CO 


^* 


C 




o 




•— V 














^ 


> 




o 


^ 




u 


+-> 







>^ 




^ 


(U 


(U 


"o 


z 


ffl 


- 




a 


-d 


u 


u 





CO 





C 


M 


CO 


^ 


+-I 


>««i 


CO 


^ 


(]) 




n 


^ 




U 


(U 





ffi>^ 





^ 




OJ 


C 


z 







■^^> 

CO 






+-» 






CO 


tw 


■M 









c 


■M 


»-H 


C 


, 


CO 


OU 


cu 


K 














in 




•<4- 




(U 




J3 





CO 



4(17 



Chapter 12 



STEAM 

Properties of Water Vapor 

THE water used in the generation of steam may be present in the boiler 
plant in a number of different forms. It undergoes various transforma- 
tions in the boiler or in the auxiliary apparatus used in the boiler plant. 
In this chapter the nature of water vapor is explained, and tables of the 
properties of steam are given, accompanied by a demonstration of their 
application to practical problems. 

Entropy. In solving thermodynamic problems a mathematical ratio, 
considered as a property of substances and known by the name entropy, is of 
value. Most, if not all of such problems, can be solved without the use of 
entropy, but engineers are now generally convinced of its advantage. It 
should be thought of, however, simply as a mathematical expression. 

It is difficult to give a comprehensive definition of this property. One 
that will answer the purpose here is that for any reversible operation an 
infinitesimal change of entropy is ecjual to an infinitesimal change in the 
quantity of heat divided by the absolute temperature at wdiich that change 
takes place, the transformation being so small that no change of tempera- 
tL're can occur. Thus changes only, of entropy, can be measured. Expressed 
as an equation, 

d<p = -^ (43) 

in which 4> is the symbol for entropy, // for quantity of heat, and T lor 
absolute temperature. Any finite change can therefore be found by integrat- 
ing this expression between the proper limits. Rewriting it in the form, 
dH = Td4>, gives a simple expression for heat in terms of the temperature, 
an easily measured quantity, and of the change of entropy. Tables are calcu- 
lated or charts constructed, giving changes of entropy. A measurement of 
the temperature and a knowledge of one other property, as the quality or 
^■olume, in order to determine the change of entropy, are all that are 
required to find the quantit}^ of heat. 

Isothermal Expansion. If a substance, while expanding, has sufficient 
heat added to it to keep the temperature constant, the process is termed 
"isothermal." The pressure and temperature of saturated steam will vary or 
remain constant together, while if an ideal gas expands with the temperature 
constant, the pressure varies inversely with the volume. 

Adiabatic Expansion. This is an imaginary change supposed to take 
place in a substance placed inside of some vessel, as a cylinder, all the 
walls of which are of non-conducting material ; consequently, no heat passes 
through the w^alls to the substance or away from it. It is isolated from all 
outside heat. Work can be done, however, by drawing on the energy 
already stored in the substance. 

A reversible adiabatic is an imaginary change taking place without 
friction or other actual losses. When the direction of such a change is 
reversed, all the accompanying heat changes are reversed. Upon completion, 
everything affected by the heat changes in the original direction will be 
returned to its initial condition as far as heat is concerned. This applies to 
the working fluid and to substances outside as well. An expansion or 
compression of this nature takes place at constant entropy. 




A part of the 3500 H. P. installation of Heine Boilers in the 
Equitable Office Building, New York City. 



STEAM 



409 



Characteristics of Vapors. When a substance changes from a liquid to 
a gaseous state it passes through an intermediate condition in which neither 
the laws of liquids nor those of gases are applicable. While in this interme- 
diate stage, the substance is known as a vapor. 

A saturated vapor is one that can exist in contact with its liquid ; 
withdrawal of heat, however small the amount, will cause some of the vapor 
to return to its liquid form. The saturated condition extends therefore 
from the time when this vapor first begins to form from the liquid to the 
time when a state of complete vaporization is reached. 

The vapor is dry-saturated just at the instant of complete evaporation. 
During the process of vaporization it is known as wet-saturated vapor. 

When a dry-saturated vapor is further subjected to heat, its charac- 
teristics gradually approach those of a gas and it is then said to be in a 
superheated state. 




^^^^^^ 



Fig. 197. Perfect Vacuum surrounding Cylinder containing 
Free Piston and Liquid. 



If a closed vessel, provided with the means of measuring pressure and 
temperature, is filled with saturated vapor it will be noticed that for any 
given pressure only one temperature of the vapor can exist. Any change 
in pressure will cause a corresponding change in temperature. Therefore, 
only one of those quantities need be known to locate the others. This 
condition applies only to saturated vapor. 

Formation of Vapors. Imagine a free piston, of known weight, in a 
cylinder, containing a pound of liquid (Fig. 197), the whole apparatus being 
surrounded by a perfect vacuum. Imagine the temperature of this liquid to be 
that of melting ice, 32 deg. (This is universally recognized as the datum 
temperature from which such measurements as heat and entropy are taken). 
The weight of the piston will impose a certain pressure {p) upon the liquid. 
If heat is added to the liquid the temperature will have to increase to that 
corresponding- to this pressure (p) before the process of vaporization can 
begin. A rise in temperature will be the only effect of this heat addition, 
until this temperature is reached. (Any increase of volume is small enough 
to be negligible and the pressure (p) will, of course, remain unchanged.) 

If more heat is applied at this point vapor will be formed. During 
this process the temperature will not change ; the weight of the piston re- 
maining the same, the pressure will be constant. The volume occupied by 
the substance will increase and in so doing the piston will be gradually raised. 



410 S T E A ^r 



If a sufficient quantity oi heat be added, complete vaporization will 
result and the cylinder will contain dry saturated vapor, the liquid having 
disappeared. Beyond this point the temperature will increase, the piston con- 
tinuing its upward motion. The process has now reached the superheating 
stage and can be continued indefinite!}'. At first, as the vapor leaves the 
condition of saturation, its characteristics will continue to show a marked 
dift'erence from those of gases; as higher temperatures are reached this 
difference lessens and finally the superheated vapor takes on all the attri- 
butes of and becomes a gas. The pressure remains constant during all three 
processes — ^the heating of the liquid, the vaporization, and the superheating 
of the vapor. 

Saturated Vapors. The heat necessary to raise the temperature of one 
pound of liquid from 32 deg. to any higher temperature is known as the 
heat of the liquid. It can be calculated by the equation 



r 

J 32 



q= / Cedt (44) 

J 32 

hi which q is the heat of the liquid, and Ce is the specific heat of the liquid. 
The entropy of the liquid above that at 32 deg. can be found by integrating 

T 



-f 

J 492 



»= = / ^ (45) 



in which cte is the entropy of the liquid above that at 32° F. (492 deg. abs.), 
Ce is the specific heat of the liquid as before, and T is the absolute tempera- 
ture. 

The specific volume of a liquid (cubic feet per pound) is considered 
to be a constant quantity for all temperatures and pressures and is represented 
by 8. The density (pounds per cubic foot) is the reciprocal of the specific 
volume. 

Tables giving the properties of saturated vapors for different pressures 
and temperatures contain those of the above quantities that are not constant. 

If a pound of liquid is complete!}' vaporized at constant pressure and 
temperature, the heat necessarily added is known as the "latent heat of 
vaporization.'' and is expressed as L. This was first found by experiment. 
From such experiments empirical formulas have been derived, l^y means of 
which tlie values in the tables have been calculated. 

The increase in entropy during vaporization, known as tlie ''entropy of 
vaporization," is found by dividing the heat of vaporization by the absolute 
temperature. Its expression in symbols is 4>s or L/T. 

The sum of the lieat of the liquid q and the lieat of vaporization L, is 
known as the total heat of drv saturated vapor and is represented by 
H. 

H = q^L (46) 

Similarly the total entropy is 

<t> = <Pe +-y^ (47) 

Wet Saturated J'apor. If suft'icient heat is not added to complete the 
process of vaporization, liquid and vapor are mixed. The part of such a 
mixture existing as vapor is known as the "quality" and is designated by the 
symbol x. The part remaining as liquid is the ''wetness" or moisture. In 
most types of boilers the quality of the steam produced is from 98.0 to 99.5 
per cent and the wetness from 0.5 to 2.0 per cent. The water is then held in 
suspension in the steam as a sort of fog. It does not affect the temperature 
and can be carried an indefinite distance by the steam. 



S T E A 'M 41 1 



The properties affected by this partial vaporization arc the heat L, the 
entropy L/T, and the specific volume. The last can be expressed as follows •. 

Sp. vol. = X V + {\—x) 8 (48) 

=:x{v — h) + 8 (49) 

in which v is the specific volume of dry saturated steam, xv the volume 
of the steam present, and (1 — x) 8 that of the wetness. § is small (0.02 cu.ft.) 

SnperJicatcd Vapors. The properties of superheated vapors are calcu- 
lated principally from laws similar to those applying to gases ; thus the 
addition of heat during the process is Cp(/sup« — ^sat-). The increase in 
entropy is <:p*loge'(Tsup-/^sat.)» when Cp for both expressions is a mean 
specific heat for the given range of temperature. The specific volume is calcu- 
lated by using the characteristic gas equation worked into an empirical form 
as the result of experiments. Tables for superheated vapors usually give the 
total heat //, the specific volume, the entropy * measured from that of 
water at 32 deg., and include these quantities for the liquid stage and for the 
saturated vapor stage. 

The foregoing discussion of the properties of vapors, although intended 
primarily for use with steam, is equally applicable to other vapors ; for exam- 
ple, ammonia as a refrigerative fluid. 

Properties of Steam. Steam is usually generated in a boiler in which the 
vapor is removed as fast as it is formed, thus keeping the pressure constant. 
Water is pumped into the boiler and must have its temperature raised to 
that corresponding to the boiler pressure before vaporization can begin. If 
the temperature of the water is 32 deg. when it enters the boiler, the heat 
of the liquid will be added to each pound previous to vaporization. If, as is 
usual, the water is at some higher temperature when it enters the boiler, then 
the heat added to each pound previous to vaporization will be the heat of 
the liquid at the temperature of the boiler steam minus the heat of the 
liquid at the entering temperature. 

If more heat is added to this water, steam is formed. This process 
may be complete, producing dry-saturated steam, or partial when the steam 
is wet-saturated. The quantity of heat added is the heat of vaporization 
(L), or (xL) respectively. 

The process of superheating due to the continued addition of heat at 
constant pressure may take place in a coil of pipe placed in the patli of 
hot gases inside the boiler setting, called an attached superheater; or in a 
coil placed over a separate furnace, known as a separatel3^-fired superheater. 
With either type the heat per pound above the point of dry saturation is 
the mean specific heat for the temperature range multiplied by this increase 
in temperature. The method of determining the increase in entropy during 
superheating and the specific volume of superheated steam is described else- 
where. 

Sources of Data. Most of the properties of saturated and superheated 
steam have been derived from experimental investigations extending over a 
long period of time. The scientists of later years have produced more 
accurate results than did the earlier workers. No attempt will be made 
here to give in detail the work of these experimenters, since it is taken up in 
the standard works on thermodynamics. 

When authors of steam tables have used different equations as a basis 
of their computations, the results will vary somewhat. In recent tables, 
however, these differences are negligible for ordinar}- engineering work. 

The following problems will serve to illustrate the use of Tables 62 and 
63, which are extracted from "Properties of Steam and Ammonia,'' by 
Prof. G. A. Goodenough. 

Example 1. How many heat units will be taken up by the water in a 
boiler per hour if 10,000 lb. are fed per hour at a temperature of 153 deg., 
the boiler pressure being 150 lb. absolute, (a) if the steam is dry-saturated; 
(b) if 2 per cent priming is present; (c) if by the use of an attached super- 
heater the steam is superheated 70 deg. ? 



412 




o 

u 

o 



U 

c 






o 
c 



cu 

X 



o 






o 
a 



STEAAL 413 



(a) Looking in the tables under 153 deg. we find the heat of the liquid. 
q z= 120.9 B.t.u. This heat is already in the water when it enters the 
boiler. If the steam leaving the boiler is dry-saturated the heat H := q -\- L 
will be present. This we find (opposite 150 lb. in column 7) is 1194.7 B.t.u. 

The heat taken up by the water in the boiler will be the difference 
between that in the steam when it leaves and the water when it enters. 
This will be q [150-Ib.] 4- L [150-Ib.] — q [153 deg.], or H^ [150-lb.] — 
q [153 deg.l per pound; substituting and multiplying by the weight we have 
10,000 (1194.7 — 120.9) = 10,738,000 B.t.u. per hour. 

(b) If the wetness is 2 per cent then x = 0.98 and the expression will 
be: q [l50-lb.] + 0.98 L [150-lb.] — q [153 deg.] = B.t.u. per pound. Then 
10,000 (329.8 + 0.98 X 864.9 — 120.9) = 10,565,000 B.t.u. per hour, when 329.8 
and 864.9 are the values of q and L for 150-lb. pressure. 

(c) If the steam is superheated 70 deg. its temperature will be the 
temperature of saturated steam at 150 lb. pressure plus 70 deg. Opposite 
150 lb. the temperature is 358.5 deg., therefore the temperature of the 
superheated steam will be 358.5 -f- 70 = 428.5 deg. 

The heat content of this superheated steam is found in Table 63 under 
150 pounds and opposite the 428.5 temperature. Interpolation between 420 
and 432 deg. will be necessary. 

H = 1235 B.t.u. 

The heat taken up by the water will now be, 

H [150-lb.] — q [153 deg.^] per pound, or 10,000 (1235.0 — 120.9) = 
11,141,000 B.t.u. per hour. 

Example 2. Find the number of cubic feet of steam that wull leave the 
boiler per hour under the three conditions given in Example 1. 

(a) If the steam is dry-saturated the volume of a pound can be found 
opposite 150 pounds in Table 62, Column 4, giving v = 3.02 cu. ft. Total 
volume = 10,000 x 3.02 = 30,200 cu. ft. per hour. 

(b) With 2 per cent wetness the volume of one pound will be found bv 
the formula x (v — 0.02) -\- 0.02 = 0.98 (3.02 — 0.02) + 0.02 = 2.96 cu. ft. 

Total volume r= 10,000 X 2.96 = 29,600 cu. ft. per hour. 

(c) If the steam is superheated 70 deg. the temperature will be 428.5 
deg. as determined in Example 1. 

Using Table 63 (under 150 lb. and opposite t = 428.5 deg.) the specific 
volume is 3.36 cu. ft. 

Total volume = 10,000 X 3.36 = 33,600 cu. ft. per hour. 

Example 3. Steam under a pressure of 175 lb. absolute and a tempera- 
ture of 440 deg. expands adiabatically until it is dry-saturated, (a) What will 
the pressure then be? (b) If the expansion is continued until the pressure 
is 50 lb. absolute what will be the final quality? 

(a) During an adiabatic expansion the entropy remains constant. The 
entropy of one pound of the steam for the first condition is given in 
Table 63 (under 175 pounds pressure; opposite 440 deg.) as 4> =: 1.6045. Tliis 
must equal the total entropy of dry-saturated steam at some lower pressure. 
In Table 62 the last column is examined until the same figure 1.6045 is found. 
Opposite this in column 2 the pressure is given as 100 lb. absolute. 

(b) When the expansion is carried to 50 lb. abs., the final quality (x) 
can be found by equating the total entropy of this wet saturated steam to 
that of the steam in the initial superheated condition. Then 

4>e [50-lbs.] + .t-~ [50-llx] = 1.6045 

In Table 62 opposite 50 lb. pressure, columns 8 and 9 respectively, we have 

L 
T 



4>e = 0.4108, -f:^ = 1.2501 0.4108 -^ 1.25014- = 1.6(H5 



X = 0.955 



414 S T E A M 

When extreme accuracy is not necessarj-, graphical charts can be used in 
place of the tables. The use of two of these charts. Figs. 198 and 199, is ex- 
plained below. 

Temperature-Entropy Diagrams 

T^HE diagram, Fig. 198, is given by Prof. C. H. Peahody to solve problems 
-■- in saturated and superheated steam. The abscissas are units of entropy 
and the ordinates are degrees Fahrenheit. At the left is a scale of pressures 
by aid of which the nearest degree can be chosen for use in the saturated 
region ; in the superheated region constant pressure lines are drawn and are 
numbered near the saturated line, as 100-lb. (pounds). 

The saturation line (which separates the saturated and superheated 
regions) gives the entropy of drs'-saturated steam, 4>e + L/T. The dotted 
lines give the quality x; the values are numbered at the bottom. In the 
superheated region the dotted lines give the superheat or excess temperature 
over that of saturated steam at the same pressure. 

The heat contents q -J- xL are given hy full lines lettered '"B-tu."" which 
slope toward the right downward. 

The specific volumes are given b}^ full lines lettered '"Cu. Ft," which have 
a moderate inclination from the horizontal. In the superheated region the 
lines can be distinguished b}^ sighting along them. The use of the diagram 
given in Fig. 198 is illustrated b}' the following examples : 

Example 1. Given the absolute pressure 160 lb. and the wetness 2 per 
cent (> = 0.98) : Find the entropy, heat content and specific volume. 

The nearest temperature is 362 deg.. and this line intersects the quality 
line X = 0.98 at entropy <t> = 1-54. The B.t.u. line intersecting this point 
is 1175 B.t.u. z= q -\- xL and the specific volume line for 2.7 cu. ft. also 
crosses this point. These figures are of course obtained by interpolation. 

Example 2. Given the absolute pressure 160 lb. and 100 deg. superheat: 
Find the entropy, heat content and specific volume. 

The pressure curve 160 lb. in the superheat region cuts the 100 deg. 
superheat line at entropy 1.63. The intersection of tlie heat and volume lines 
give H = 1250 and specific volume ^ 33 cu. ft. 

(Adiabatic changes during which the entropy is constant are represented 
b\' vertical lines, while isothermal or constant temperature changes are hori- 
zontal lines.) 

Example 3. Steam at 120 lb. absolute pressure and 100 deg. superheat 
expands adiabatically to a temperature of 142 deg. Find the final quality and 
the final specific volume. 

Tlie 120-lb. line crosses the 100-dcg. superheat line at entropy 1.65. This 
property" is constant during the change, therefore following down the vertical 
entropy line 1.65 until the horizontal temperature line 142 deg. is reached, 
we read the quality as 0.86 and the specific volume as 100 cu. ft. 

MoUier Diagram for Steam 

THE Mollier diagram for steam, as found in Goodenough's tables, is shown 
in Fig. 199. In this diagram lines parallel to the coordinate axes 
give values of heat content and entropy, as read on the scales along the 
margin. Constant pressure curves slope downward and to the left. In the 
region of superheat constant temperature lines curve gradually toward the 
left downward. These are replaced in the saturated region bj* constant 
quality lines. 

Any point on the diagram represents a definite state of the fluid. If the 
point lies in the region of superheat the heat content, entropy, pressure and 
temperature are read directly. In the saturated region the quality is given, 
but the temperature must be obtained from the pressure. 



£ UJ (^ ^ pM (£< £ ^ pM 

6 3 3 3 3' 3 3 3 3 




1.5 1.6/ f f /1.7/ / / 1/8 y 1 


.9 2.0 2.1 2.2 


'-""" /Wr-^W^ *(] -h' -fk' St^-fr-h'^h' ' 


. __ _ -- 1 - 57^ 






1 X'/ 11/ TW^ ^ 7 J 1\ 1 s 1 Al Jl_ l' 




^ Ui l/v '\/ n^ir* /h / / V /'/ \' /\ // »J5J 


" 


^, l*L'\ ,.)L./ a "''R^l T WF T ITI fK" " 




J '^/'5?//v ,:5y5/^ l^^L'^iih i ■ i ITKr 


------ _ _- -- _ — ::-650 


1/ f '/ I'S^i n^I i)^ Tt^ i ^ T ur i^ 








1 l\ > M«^V / / l^r I/ClP l^^l ^T "nTl V^ 




J. ' /\ f^ // / ikTl Ktrl 1 IJ iL \ iViX 




Li 1 ' /i / i^Hj \ 1 /aI / */ f 1 \ ^flP r/ 1. ^' 1 


. _ _ ^Q 


' 1 It I ViT) Y // \/ a/ / f "^/f ur f-^Jl 




I— 1 / ' / r' / 'M/ fX //' !)( /M / '/ \ /jW" r // \ *^ n 




1 A '/ f Vr r w / vH In vliX.^ 1/ 1 /^/ V w i y jf 1 




' ' /\tt »i ' /* /l Kt 1 ri, \ f /I/ N' F /^ /[ 1 SLi l 




' "1" ! ' /i v^ / i / « \ ' 1 »^ 1 Ji' rHL lA a / r Tf il / i/ 1 


: " ~ — ~~ ~ — 510 


1 [/\ r ' WVlj 'i V/li Afrlrv // 1 ^'/r ■1/ 1 




1 iX i 'f 1 \'/ lyf rIV I i ir ^l]\ 1 1 1\ \— 




I k ^ fi^ 1 1 1 1 \l vx //kA r \ ~]rr TT -^ h1' 




' "/> i // Wi / r //'//' i/ i/j 1 ] '/ / jOl 4 3^ 




v//l }nJ \l 1^'' l\l ) 1 IVt IS iv *' l\ 1 »! 


. - -___ _ - _ ^QQ 


y V/ /v \b^\ n \l 'I / y L t I 1 Ix'mJ 1 4 / it 




1 'f n* \'ll\ r\ ir 'ill 1 Oi 1 f t k i P Jtfl 1 1 




A / ' 1 V/ r /r( M ' ' ; / d l i i \flln *i / ft 


" 


1 1 / ^ ' / ^ /' V '/ 1 '' Tn. y () \Jliliri v/iA 




1 > \' /i V / 1 //\ 1 i f\' /i 7ft ' H \i\ 1 »7 / lyiii jj 


- _ __ ^rJ^J 


m/i lt\li\ 1/ V/'/'i^s^ [/ / a/ / iAI/ "* \ii 




/ r-l \ til P'i \l V'y l\l\t I "t^ j/i 1 flNi^lVil 


" 


1 r /\SJ// I / /' / 1//'// 11? I 1 4 S L I I 1/ 1 ^ 


■ 




_____ -/<rA 


'1 / \ V \h /v 1 /n / / A 17 \ j/ / \ J / f S/l X /* 


_^_ ^^g 


?y /l V/ V / r* Hint I l\li Vl/ 11 A / / ^u/' i^> ^'^ 




0, / 1 /V fN 'An/ 1 fl/lM 1 li 1 / 1 f sfi _fl- v'^i 




i^r?ivrv\ /V"y1v>^/^7^/ t i ^ i ^t \^/r / 




■J.P,'^yl\K^il> r // U ii<JlillU // J / W f J , Vfc' A 


ylQA 


310 '^- \v tv^^/i *;/ , /7 7 v/ iMf'ifl/ /\// ■"' 7 / v^-^ ^ 


^^y 


«u [y \y uv ,^A y / ' /' llUH-j}^ 1 ' '' H?^A i 




^^n r\\i-A'^^- c^)A M / /^ l^ ffW ir^ h ) \<ir 




300 »s^^A\i^/ fii\ J \iW K -frj ii h L-vT/ 


u ip'- ~ : ~:~: 


275 ^^^^^\W:-M4ml^l4-^M^^ 


JL ^JQ 


.50 h^Sz)^4M^lzzi^^^^^^ 




*-^ ;«4M.\,. \ic$MXK/A-- -v4^ U V \/ X ^ iatjiit 


rtt 


-^p \'^i>K^''-\j iM/ifivy / >^ iY J 1/ W w i \ HA/ 


I 


"5 *^^Q^V^My/A?/ \ l^ I h tf> t \ n \ i \.l\ 




v-vnN yG/J^J^ / rr/ \/ ^ /r ' > // Ji 


.4- 1""::- : 390 


200 23^^-^iS?>a§'/ 4 ^f^ t'hiu H^ ^ X kIj if 




'" TLsC^-^ jJaF/wa/ / J^ C>i --SL Ix^^ t^M I^ 


1 


ifiA £r--it^Li^5^M tv/ 5^/ ^^i-A-H 3\-- af-t^ 


1 


SRiT" > yKJ i ^^f rT / C J 5 \ Tn T 






:q::~:~~ , " ~ - - - -__-g,^Q 


'if ji — tH'^c' •r^ I'TTr \ ~hi~' T~TVii~r~rr^ 7~1r1" 


._L_ 


liA Q ^ ^hS^^^\}^i\nf\ff~i\ di it w /'^7" 


3. 


A^-jjt:. - r r V rrv e67 v "ff ' N ' n 11 i ' it ""'I is 


^1 . - OCA 


[ ^\\1 r V \ ^ ^ \ ^ "*T 3 JuTrv / r i ^ /jT' // Y y jP, •H/ f > 


.A- __ - _- _ Z_IdO0 


19ft ij j:j5;:;:i:iSjS/s-3«~3:s] ]: pjr t^ji sr± 


vx-- _- _ : : 


uo ^'^ \^ ? \\^7l^'Y,~jj^t 11 ^\ f w ^jt^hl 






■^~ 


i\ v \\ '^"^ci* 1/ L-^!^\L i\ "* ^ ■ i\ ik *"/ B^ 




100 'r' -c"!/ \S* CVlf jLaI Hi A ^ "* "M^ /^ li II \ 1 I '^ 


in: ooO 


"T* ^ \ . ^ \ \^u' \ i f^l I \l f u ^ STT|~in ft ^ r T ' 


■*^_ 


90 'f=^-K ^Jv^^JAuMa./^^ L W i-!!_^3f::*j(-- 


\i3t_ :_: _^_"~ ~ - _: .-js 




.".^i - - -- -- - _ C 


*0 \ 5> A^T^f 'vT^-i^ 7/^)/ J ^/ '^ N/ K Ih 1 


_ji oi A«fl 


:^-C^?a\ ^L-i\u.ti:W^2^U L l^Jj L l^^dJ-^l 


n - - - - - I - I I — 3i0o 


70 ,.B\^^^, »d\ ■^"vrR?^^ Wt^ nil ^ T v^ ^r 


. [. - ___ -_a> 


lS'^-c"T^\ V^^\/) ^ (/ ^T ^T* ? 


-^X _ - _ _- _ 2 


an i-pSS-J-SC3^ \ |5_j7^JI/ X ^ i X d'<ii ^ J 


sjX - X_ _ Xi 


cObi '2^_Slj2Z^^ Sxgrt/n^ct.ii j ^c jl ^ <«; 


.11 _ _ OOA c4 


^^ \^ \ \i \^''^^^^\Alli .^'^^ } 1 * f T /1 v^ 


-fL ._ _ __ _ ^90^ 


-« \ ^»._J^ \- ^.13_St^''V-<s7^ ESLISj I IZ VvV 




50 ; = H_^^,^.^<-^_^vM-^/ P ^^^- H!:f::\^^^ 


^-JuLi:::::::::::::::::::::::::::::: « 


:a:^::5i::^:^iiitS^r" i:/ t ^ ^^r:/^ 


vi:^ ±: ii___ _ __:_ _:^Af7n5 


f-40-i-k, N ^ V ^jyv^Vt^ M "trr^ 1 1^ 1i^T 


^ .m : 270*^ 


«S ^" ,._>:jv.it.?-2^^^,T:k:^r. §,^,_'7v A ■it ^ii-^' 


^t^ - 2 


Si 35 ii-j^'v^^ S\ AA^ vS V ^^ u.mS t zit it tj i 


^ t ni 


a 11 t-^^\^\-4m^KA^f^^ 


3 2i "' ~Z o. 




' \\\- ^^'A^\ V v^ly>»^^'iy n ^ ■ /' / /^ 


Sj:st~~ "" "'" ""- " " — :::260g 


i5-„,^^3\\\^ \^ \ ^vN^v^-^ V u^ r i V ■ /Ui 


."li JL _ - - 4) 


cJj 25 ---Sa ^qiKL._iX^ijt:!5rS: 5 S-JL5 ci ^i ^'cpf 


^4// it - - --- H 


^ ..5i^ji-j=^^n:!^\_Vr s i,^.j:E^LL, 2 &L-^t 




fc j:f^_H_N^_^ j^ Jffiv:^^^ 


= 3- = I 230 


S.2;:;::5:?r:5::g^a:HJ^^^:^S=^K^;-^--SS 




. 18. V, ^^,)i^^^<r-^^l^ 'S.^'^KSZ^^t^ i XXJD 


/ ^1 


«2 ia:'fe = c: S-^-tiT VsLTT^ Vs xS lS jtt ^t ^ ^xx 


N / /l" 


iO »5 ^'sT^ ^ xKi'^ V^ K^ tTS S^^\ ^ T- 1 1w i ' 




^ Mr-U-rV-\ v\uV \t\A^\^\6\juNL^s, cJl^. t /'\.-/ - 


■^;: [t: " " "": — — :~ "~:2io 


- 11 :<.^^. \\ \^ J\T\ \ xXjV^ ^r^s^-er ?l ^nr S u -^^f-*- 




c *' ^ZlSx'v^ Mi3-^=r^v=e 'TX^--v-^Ojr^"s4<S ^ i 


H 1 


•-' 10 ,=.i*^-A^4s5:=S J_s , Sa ^^ ^ ^).i^ivi^)>MJ<i^-Ji- -^ 


Ibl I 


. iO;*i-»^ ''.v ^o-fxr .^ ]^ \v ^. i^^I}'%f^t W ~ 1 


> ^ .JJls 1 - . - - lOrt 


g 9 ^'^^^J^-p^'^^--^-^g=s-!5^_g=p,,4 


t-l^^ - - -_ 1>W 




f^l^'ll 


£ 7 ■ - \ , VK, i ik V A V> ^ , R . "^ ^ •Pr^T' 1 Vt^ , ' // 


J 1 


6 ir V. VK ^\ V. A A ^^J .'. ^tii^iM^^t**-^ fr 


.l/SiA_ jC 1 170 


I ■^^^r\-\-r^4^-^^^-P^^^=1^''-vf»<iV^-/*hP' 


.mi-lir ij: wu 


^ ipr-^^HV^^T^'^. N k\ \\ \^ v^ "^ s '«OjW-^"( Mfl- 




,v s^^ ^.\ sK S\ x^ ^. LA-^\:^^ = ^^^sS rvWli? 


/ lJL l 


4 :§4_N. N^,^; A3,t-b5;''i-''5-^^-^(i^(^ 


Lg/^X j-l :p 150 


3 g^M^^Wwj^lg^ 






;S5Sl5::::: :::+::: 


. ^w^TOiroJn^W^^^o^ 


zi-tii.^ ±_± jQQ 


'TOWTO^^Pfe^^^^ 




,5 :55r-^— ^^-^sf ^t-^s3±iv-5=i^^5^-'^;s''^^dS 


" ^ s _k ^M- ^ " 


tn > ■ "^ rw+^rt-rF'^4lMTN Pm. HsHhYNm 


"nil 'Nt Ci/l . . ._ _| itA 


^--^"■•\ ^. A v \ ^ "^i rVi "^o ^\ -^22 


J-jUvrVjN/tl . - - - 2jy 


:>__^s--^c--^> -V+^^-X _^__%-P^^=^^=^ici^: 


.; 1 K S Tsil - _ 


H-f\N-44i>. - Tit - ^^ \vH^^HiT^ ht >J % > '>. 




"l^^^^^^W 


;-^XNX^;:|^;^ -L ^ 


. ; 0vS%^:-^-^^.4P«^--5^ 


=^^#^=¥^t^s--"-"-""=-" ^^ 


'^•«^:?£:^5^'^|l^ = ^:^:^^S#^<Sv::i:: = ^ 


^;-^i-^%--!ttS;::::::±:::::: 


, - . ,^ L . !^ . Sfc - , . s ' N <■ V ■>. X \ >lV.^. ^ . '."v r\,^.. 


. 53 ^ X iii.1// ^ ^ '';>nrtiiritUKt-^r-- - - tu\ 




:5 Sm^.^^S^,;,--:-:":: ^ 

5 -s^^^jjL^ Sw->^^v •^-/^^c*♦^. 


1.6 1.6 1.7 1.8 1 


9 2.0 2.1 2.2 ^ 



Fig. 198. Peabody's Temperature Entropy Diagram for Steam, 




AdOUlN3 



STEAM 417 



To prevent confusion, the volume curves are not given. This property 
can, however, be easily obtained. If tlie point lies in tlie superheat region, 
read the pressure and temperature from the diagram and look up the corre- 
sponding value of volume in Table 63. If it lies in the saturated region, read 
the pressure and quaHty from the diagram, look up the specific volume of dry- 
saturated steam at the same pressure in Table 62 and multiply this by the 
quality. 

The following illustrations of the use of this diagram are given by 
Professor Goodenough. 

Example 1. Find the properties of steam at a pressure of 120 lb. abso- 
lute and a temperature of 412 deg. 

From the diagrams the point that represents the state of the steam is 
found at the intersection of the curves p = 120 and t = 412. From the 
scales are read H = 1231 B.t.u., * = 1.637. From Table 63 the specific 
volume is found to be 4.16 cu. ft. (These particular values could be found 
as easily and more accurately from Table 63.) 

Example 2. Steam at a pressure of 120 lb. absolute and a temperature 
of 412 deg. expands adiabatically. At what pressure does it become dry- 
saturated ? 

During this change the entropy remains constant ; hence the final state 
is given by the intersection of the line <p = 1.637 with the saturation curve. 
The pressure indicated by this point is 68 lb. per sq. in. absolute. 

Example 3. Steam in the same initial state as in Examples 1 and 2 
expands adiabatically to a pressure of 2 in. of mercury. Find the volume, 
heat content and quality in the final state. 

The entropy in the initial state is 1.637; hence find the intersection of 
the line cp = 1.637 with the curve /? = 2 in. of mercury. This point gives the 
values X = 0.815, H ■= 913 B.t.u. From Table 62, v for 1 lb. absolute 
(which is practically 2 in. of mercury) is 333.3 cu. ft. ; hence the volume 
of the mixture with a quality x = 0.815 is 0.815 X 333.3 = 271.6 cu. ft. 

Flow of Steam Through Nozzles 

The ordinary form of nozzle in which steam expands as it 
passes to the blades of an impulse turbine is shown in Fig. 
200. Suppose steam is flowing through the nozzle, the pressure being 




Fig. 200. Expansion Norzle. 



Pi, Pt, P2, as indicated by the three gages. As long as the absolute pressure 
at Pi is less than 0.58 of the absolute pressure at Fi, the absolute pressure 
at Pt — the smallest section, known as the throat — is exactly 0.58Pi. When 
P2 is less than Pt the weight of the steam flowing through the nozzle will 
not change. This weight is entirely independent of any pressure beyond the 
throat as long as it does not exceed the pressure in the throat. 



418 




U. S. Realty- Building, Ne^. York, N, Y., containing 1525 H. P. of Heine Boilers. 



S T E A M 



419 



The formula for the flow through such a nozzle is as follows 



W = 



A I 



(50) 



W = Steam, pounds per second 
A = Area of the throat section, square feet 

Vt= Velocity of steam passing the throat section, feet per second 

V = Specific volume of steam at the pressure and quality in the 

throat after adiabatic expansion at constant entropy. 

On account of the rapidity with which steam passes through the nozzle, 

not allowing time for any appreciable transfer of heat through the walls, 

the process can be considered as adiabatic and the entropy constant. 

Applying the laws for the adiabatic flow of steam, the following formula 
for the velocity of flow through the throat section can be deduced : 



Vt = 224 V^i — ^t 



(51) 



Vt = Velocity at throat section, feet per second 

Hi = Heat content at the absolute initial pressure and quality of 

the steam, B.tu. 
Ht = Heat content at the absolute throat pressure and the quality 

at that pressure resulting from a constant entropy change. 

If the part of the nozzle beyond the throat is omitted, leaving it as 
shown in Fig. 201, the result is a standard convergent nozzle, which can be 
used in measuring the flow of steam within the limits of ordinary accuracy. 

The formulas for the weight and the velocity at the throat of the 
expansion nozzle can be applied directly to the simple convergent nozzle, con- 
sidering the dimensions and properties of the throat of the expansion nozzle 
to be those of the convergent nozzle, the initial pressure for the expansion 
nozzle being the pressure before the convergent nozzle. 

This makes, as will be noticed, a nozzle with a rounded approach, as 
shown in Fig. 201. Other proportions can be used, but those indicated have 
given good results in practice. 



0P. 




0- 



Pt 




<-d-> 



Fig. 201. Simple Convergent Nozzle. 



The use of the formulas can be explained by an example. 

Steam at a pressure of 140 lb. abs. and a temperature of 400 deg. flows 
through a standard convergent nozzle, 1-in. diameter, into a pipe line where 
the pressure is 60 lb. abs. How many pounds will pass through the nozzle 
per second? 



420 



S T E A ^I 





' 1 


T- 


M ' ! 


-TT"! T 


MM 


! , , ' ■ ' I 1 ■ 1 1 


1 


IM 














































































































































1 i 1 
1 1 
























1 1 












































\ 




















































































■ \ 
























_^ \ 






























i 






; 


' 


















































\ 




























































\ 
















































' 1 


, 












\ 
















































1 












\ 


' 


























\ 
















\ 




1 ' , 










1 ■' 




1 : 


\ 




\ 












1 1 : 










\ 




\ 






1 


i 




{ 






i 










A 




\ 






I 1 i 


1 


' 










1 1 

! 




\ 
















\ 




\ 
















\ 




\ 








; 1 1 ! 








\ 




\ 








1 


! 










\ 






\ 






1 


! 










\ 






\ 














1. 






\ 














\ 






\ , 


, I 1 














N 






\ 


: 








, 1 






; 


1 1 ' 


1 ! 












V 
















A ■ 
























































7- 
















V 
























































\ 






1 




\ 


















































\ 










A 
















































\ 




^ 


































\ 


. . 1 1 


, \\ 




























\ 




V 


- > 


\ 




1 ; 
















^, . i . 




^ 


£i 


L , 




. 






, , 1 










t^v ■ 


■ 1 


\ 




; 1 • 


















s^ 


1 


' 




N« 


; ! ' ' 
> i 1 


i i 
















O 

--3 


^. 1 






A 






















r\ 






*A 




, 








i ' 






. 










- :v 


V. 




r 


iN. 














! 




















^N 


<. 


1 i 1 




^\ 












1 




































^^ 


t 












\ 










1 










































*cK 


I 










\ 








1 






















j 




















\ 


4 


*N 


k_ 










\ 






1 










































1 




_ ; ^ 


-J 


Vn 






1 


s 
















' ' 




1 
























|-^ 




^c 


i 


s 






■ 


\ 






! 1 




































V 


s 








\ 














1 


















































1 


^ 


««-i 








^ 






































































'^*N 


L 




I 




'V 


V 




































































% 


k 


k 










s 


V, 








































































•n 


^ 










S 


V 












































































•^ 


^ 


K 






k 


N, 






























—i 








^ 








_j 




















L 


u 




u 




□ 




d 




^ 




-J 1 



'^ 



»<> 






Ci 


5 






%j 


T. 




^ 


■j: 


^o 


X 


n 


ci 


^ 






•«* 


^^ 




<; 


— 




•>> 


T. 




1? 


S 




QN 


z 


K 




'u 


Ci 


5 


^ 




^ 


•rJ 




^ 


s 






Xfl 




^ 


!_ 




«ti 





«0 




1 

E 




< 


o 




^ 


r^ 




Ci: 


is: 


On 






Ci 







o 



9> OOh^^in ^K>C^4— . O 

ci d d o q' o' c» d o o 



STEAM 421 



Using the Mollier chart we find that steam Pi at 140 lb. abs. and 400 deg. 
has a heat content of 1221 B.t.u., and an entropy of 1.61. The pressure in 
the throat of the nozzle, Pt will be 0.58 of 140 lb. or 81 lb. abs. As the change 
between these two pressures is adiabatic we follow the 1.61 entropy line on 
the chart until it intersects the 81-lb. pressure curve. Here we read the heat 
content as 1173 and the quality, x = 0.987. The specific volume at this pres- 
sure and quality is 0.987 X 5.42 = 5.v35 cu. ft. 

The velocity in the throat of the nozzle will be : 



Ft = 224v' Hi — Ht = 224 i/ 1221 —1173 = 1552 ft. per sec. 

The area of a 1-in. orifice = 0.00545 sq. ft., so that the weight per second 
will be : 

W= 4^= 0.00545 X 1552 _T^i^ 
w 5.35 

In solving this problem the final heat content in the velocity formula is 
taken at 0.58 of the initial pressure, which is the pressure at the throat of the 
nozzle, and not the final pressure in the pipe line. These formulas can be 
applied to either superheated or saturated steam. 

As a result of experiments, empirical formulas have been derived for 
the flow of steam ; these are sufficiently accurate for engineering purposes. 
Two sets are in common use, one by Napier and the other by Grashof. 
Napier's experiments were made on dry-saturated steam and his formulas 
apply only to steam in approximately that condition. He found that : 

W = '^£^ when P. = or < 0.6Pi (52) 

JV = O.O292.IP2 (Pi — P2) when P, > O.6P1 (53) 

W = Amount of steam, pounds per second 

A = Area of orifice, square inches 

Pi = Absolute pressure before orifice, pounds per square inch 

P2 1= Absolute pressure after orifice, pounds per square inch. 

The first of these gives results accurate within 2 per cent. The second 
formula is not to be recommended as accurate within 8 per cent when Pn/P^ 
is 0.85 or higher. 

Grashof's formula for dry-saturated steam when P2 ^ or <^ 0.58 Pi is : 

A p,n.97 

W = ^^ (54) 

For a given nozzle, the weight discharged is greater for wet-saturated than 
for dry steam. The flow then is inversely proportional to the square root 
of Xx, and Grashof's formula becomes 

A P,0.97 

^=^nA— (55) 

60 V^i 

To find the weight of steam discharged when P^ is greater than 0.58Pi, 

the curves in Fig. 202 are convenient. They are plotted from the results 

of Rateau's experiments on convergent nozzles and thin plate orifices. The 

discharge for the nozzle is first found for the condition when P^ is less than 

0,58Pi. This is done either by formula (52) or by formula (54). Then the 

P . 
ratio ^ IS found, and the lower (abscissa) scale of Fig. 202 entered with 

this ratio. Proceed vertically to the point of intersection with curve for 




Everett Building, New York City, equipped with Heine Boilers. 



STEAM 423 



convergent nozzles, and then horizontally to the left (ordinate) scale and 
read the coe.fficient of discharge. Multiply by this coefficient the discharge 
as just found, and the result is the actual discharge under the conditions 
given. 

To find the weight of steam discharged through an orifice in a thin 
plate, proceed as above, except that intersection is made w^ith the curve for 
thin plate orifice. 

Example : By the use of a thin diaphragm inserted between the flanges 
of a joint in the steam pipe supplying an auxiliary engine, it is desired to 
find the weight of steam consumed by the engine. The pressures observed 
are 152 and 143 pounds ; and the hole in the diaphragm is Vis inch. 

The area of the orifice is 0.0767 sq. in., and the absolute pressure Pi is 
166.7 lb. Then by formula (52) 

^^^ .076 X 166.7 

W = ■ =Tr = 0.18088 lb. per sec. 

per sq. in. discharge when P2 is less than 0.58Pi 

Now Pi = 166.7 and P2 = 157.7 and 157.7/166.7 = 0.946. Entering the 
lower scale of Fig. 202 with 0.946, proceeding vertically to intersection with 
orifice curve and horizontally to the left-hand scale, read as coefficient 0.31. 
Mu1':i':!ying by the coefficient 0.31 the maximum discharge 0.18088 as found 
above, the discharge through the thin plate is found to be 5.6 pounds per 
sec; multiplying by 3,600, the discharge is 202 pounds of steam per hour. 

The pipe on the supply side of the diaphragm should be straight for at 
least 10 times its bore. The diameter of the hole in the diaphragm should not 
be larger than one quarter of the pipe bore. If necessary, a larger pipe must 
be put in on the supply side with a straight length of not less than 10 times 
its bore. 

If the diaphragm is thicker than Vg4 inch, it should be countersunk at an 
angle of 45° on the downstream side, so that the parallel part of the hole is 
not more than ^64 inch long. On the inlet side of the diaphragm, burrs 
should be removed and great care taken not to round away the entrance 
corner which must be left sharp. 

Owing to the difficulty of removing the burrs while keeping the corner 
sharp, it is sometimes easier to use a much thicker diaphragm and form a 
convergent nozzle in it. The thickness of the diaphragm should then be 
about twice the diameter of the hole. There should be a parallel portion 
whose length is about half the diameter of the hole, and a curved portion 
formed to a radius of about 1^2 diameters, making a smooth, rounded or 
bell-mouthed entrance similar to Fig. 201. 

While the diaphragm method is a simple one for finding the steam con- 
sumption of auxiliaries, and so forth, it is essential that great care be used 
in getting the exact diameter of the hole and the exact pressures obtaining. 

The pressure gages used should be connected within about 12 inches on 
each side of the diaphragm. To insure accuracy, they should be tested be- 
fore and after taking the readings, and, as a further check, the readings 
should be repeated with the positions of the gages reversed. 

Experimental data for the flow of superheated steam through nozzles 
and orifices are lacking. One of the latest formulas, in the form of that of 
Grashof, is worked out from experiments by Lewicke and checked from 
data in possession of the General Electric (Ilompany. This formula is as 
follows : 

W = ^^^ C56^ 

60(1 +0.0065 P») ^^ 

in which D is the superheat in degrees Fahrenheit, and the other symbols 
are as before. 



424 



.^:.i 



Table 62. Prooerties c: 5 = rv:r=ted Steara. 



IK per 



quid 



per; 



H 



29.72 

29.62 
29.52 
29. i2 
29.32 



29 
29 
29 
28 
2S 



,22 
li 
,02 

,92 
,S2 



28.72 

25.62 
25.52 
25. i2 



0. 



^4.55 2992 



44.97 
.1965 52.67 
.2456 5883 
.2947 63 



981056 



0.3438] 
-3929' 

4:421 

.491^ 
.5403 

0.589 
.639 

.688 
.737 



28.32 


.786 1 


28.22 


0835 


28.12 


.884 1 


28.as 


.933 ! 


27.92 


.982 



27.SS4 

27.82 

27.72 
27.62 
27.52 
27.42 

27.32 
27.22 
27.12 
27.02 

26.92 

26.82 
26.72 
2-6.62 
26.52 
26.42 



68.43 
72-35 
75. S7 
79.06 
81.98 

84.68 
87.19 
89-54 
91.75 
^.83 

95.80 

97-67 

99.46 

101.17 

! 101.76 



1.031 1102.80 
1.081 104.37 
1.130 105.88 

1.179 107.33 
1-22S 10S.73 



2086 
1550 
1255 



1.326 
1.375 
1.424- 
1.474 

1.523 
1.572 
1.621 
1.670 
1.719 



110.08 
111.39 
112.66 
113.89 
115.08 

116.24 
117.37^ 
118.471 
119.54i 
120.58^ 



913 
805 
720 
632 
596 



0.000334 
.000491 
.000645 
.000797 
.000947 

0.001096 
.001243 
.001389 
.001534 
.001679 



549 ^0.0018^ 
508.71 .001966 
474.3i .002108 



444.^ 



418.2 .002391 



395.00 
374.^ 
355.7 
33&9 



333.31 

323.7 
309^ 
297.1 
283.5 
274.7 



.002250 



.002532 
.002672 
.002811 
.002950 



0.00300 

0.00309 
.00323 
.00337 
-00350 
.00364 



264.7 0. 

^3.3 

246.9! 

238.9 

231.4J 

1 
224.410 
217.8 
211.6 
205.7 . 
200.2^ . 



.00378 
00391 
00405 
00419 
00432 

.00446 
00459 
00473 
00486 
00500 



2^361074.2 
13.04 1079.2 
20731062^ 



26.91 



32.06 106&1 

36.301090.1 
4a42 1091.9 



^.93 
47.11 
3aQ8 



52.72 1097 



33.23 
57.57 
59.77 1100.8 
61.84 1101.8 



63.81 



7a79 
72y36 
7386 
73.30 



78.05 
79.36 
80621 



1083.7 



1093.3 
1095.0 
1096.4 



1071.7 0.00522.1687 2.1739 
1066.1 .0262^2.113021392 

1062.0 .0413 2.0732 2.1146 

1058.8 .(^5 2.0423 2.0956 

1056.01 .0632112.0169 2.0801 



1053.6 0.0717 1.9956^2.0672 
1051.3 .0790 1.9768"2.0558 
1049.6 .0856 1.96G:. ^ :M38 
1(H7.9 .09151.943512.0370 
10I6.4J .09691.93202.0290 



.6 1044.9l0.1019ll.9198l2.Q217 
1098.8 
1099.8 



1102.7 



65l68 1103.3 
67.46 11(^.3 
69.16 1103.1 



69.76 1103.4 



11(».9 
110&6 
1107.2 
1107.9 



76.70 1108.3 



1109.1 
1109.7 
1110L3 



81.8311110.8 
83.01 1111.4 

84.19 1111.9 
85.32!lll2.4 
86.41 1112.^ 
87.481113.3 
88-52 1113.8 



1043.3 .10631.90852.0150 



1(H23 
1041.1 

i(Mao 

1088.9 
1037.9 
1036.9 
1086.0 



1033.1 
1034.2 
1033.4 
1082.6 
1031.8 



1031.1 
1080.4 
1029.7 
1029.0 
1028.3 



0.1221 



1316 



.11061.89802.0087 
.1148 1.8882 2.0080 
.1183 1.8791 1.9976 



1.87051 



.9926 

.125411.862411.9878 

1.9833 

?790 



12861.8547 



<tl7.l 



1083.6 0.1327 



0.13i: 

.1373 
.1400 



i.^>c>o^ i. 



50 
11 



1425 1.8213 



.1450 1.8135 1.9603 



.1519 



1.8274 1.9674 



0.1474 1.8099 



1497 1.8045 1.9341 



1.9639 



1.9573 



1.9311 



1.7992? 

.1540 1.7942^1.9482 
.1561 1.789311.9454 



1027.710.1381 
.1601 




1.9427 
1.9401 



1027.01 

1026.4 .16201.77561.9376 

1025.8 .1638 1.7713 1.9351 

1025.3 .1656 1.7671 1.9327 



STEAM 



425 



Table 62. Properties of Saturated Steam — Cont. 



Pressure 



In. of 
mer- 
cury 



Lb. per 
sq. in. 

(Abs.) 



Temp., 



Vol- 
ume, 

cu. ft. 

per lb. 



Weight, 
lb. per 
cu. ft. 



Heat content 
in B.t.u. 



of 
liquid 



of 
vapor 



Latent 
Heat of 
vapori- 
zation 

in 
B.t.u. 



Entropy 



of 
liquid 



of va- 
poriza- 
tion 



of 
vapor 



H 



26.32 
26.22 
26.12 
26.02 
25.92 


1.768 
1.817 
1.866 
1.916 
1.965 


121.60 
122.59 
123.57 
124.52 
125.44 


195.0 
190.0 
185.3 
180.8 
176.5 


0.00513 
.00526 
.00540 
.00553 
.00566 


89.53 
90.52 
91.49 
92.44 
93.37 


1114.2 
1114.7 
1115.1 
1115.5 
1115.9 


25.848 


2 


126.10 


173.6 


0.00576 


94.02 


1116.2 


25.82 
25.72 
25.62 
25.52 


2.014 
2.063 
2.112 
2.161 


126.35 
127.25 
128.12 
128.97 


172.5 
168.7 
165.0 
161.5 


0.00580 
.00593 
.00606 
.00619 


94.28 
95.16 
96.03 
96.89 


1116.3 
1116.7 
1117.1 
1117.5 


25.12 
25.32 
25.22 
25.12 
25.02 


2.211 
2.260 
2.309 
2.358 
2.407 


129.81 
130.64 
131.44 
132.24 
133.02 


158.1 
154.8 
151.7 
148.8 
145.9 


0.00633 
.00646 
.00659 
.00672 
.00685 


97.73 

98.55 

99.35 

100.14 

100.92 


1117.8 
1118.2 
1118.6 
1118.9 
1119.2 


21.92 
23.92 


2.456 
2.947 


133.78 
140.80 


143.2 
120.7 


0.00698 
.00829 


110.68 
108.69 


1119.6 
1122.6 


23.812 


3 


141.49 


118.7 


0.00843 


109.38 


1122.9 


22.92 
21.92 


3.438 
3.929 


146.88 
152.26 


110.4 
92.1 


0.00958 
.01085 


114.8 
120.2 


1125.2 
1127.5 


21.776 


4 


152.99 


90.6 


0.01104 


120.9 


1127.9 


20.92 
19.92 


4.421 
4.912 


157.10 
161.50 


82.5 
74.8 


0.01212 
.01338 


125.0 
129.4 


1129.6 
1131.4 


19.74 


5 


162.25 


73.5 


0.01360 


130.1 


1131.7 


18.92 
17.92 


5.403 
5.894 


165.55 
169.30 


68.4 
63.0 


0.01463 
.01587 


133.4 
137.2 


1133.1 
1134.7 


17.704 


6 


170.07 


62.0 


0.01614 


137.9 


1135.0 


16.92 
15.92 


6.39 
6.88 


172.79 
176.06 


58.5 
54.6 


0.01710 
.01833 


140.7 
143.9 


1136.1 
1137.5 


15.67 


7 


176.85 


53.7 


0.01864 


144.7 


1137.8 



1024.7 
1024.2 
1023.6 
1023.1 
1022.5 

1022.2 

1022.0 
1021.5 
1021.1 
1020.6 

1020.1 
1019.7 
1019.2 
1018.8 
1018.3 

1017.9 
1013.9 

1013.5 

1010.5 
1007.4 

1007.0 

1004.6 
1002.1 

1001.6 

999.7 
997.5 

997.1 

995.5 
993.6 

993.1 



0.1673 
.1690 
.1707 
.1723 
.1739 

0.1750 

0.1755 
.1770 
.1785 
.1799 

0.1813 
.1827 
.1841 
.1854 
.1867 

0.1880 
.1998 

0.2009 

0.2098 
.2187 

0.2199 

0.2265 
.2336 

0.2348 

0.2401 
2461 

0.2473 

0.2516 
2568 

0.2581 



1.7631 
1.7591 
1.7553 
1.7515 
1.7478 

1.7452 

1.7442 
1.7407 
1.7373 
1.7340 

1.7307 
1.7275 
1.7244 
1.7214 
1.7184 

1.7154 
1.6888 

1.6862 

1.6661 
1.6464 

1.6438 

1.6290 
1.6134 

1.6107 

1.5992 
1.5862 

1.5835 

.15742 
1.5630 

1.5603 



1.9304 
1.9281 
1.9260 
1.9238 
1.9217 

1.9203 

1.9197 
1.9177 
1.9158 
1.9139 

1.9121 
1.9103 
1.9085 
1.9068 
1.9051 

1.9034 
1.8886 

1.8871 

1.8760 
1.8651 

1.8637 

1.8556 
1.8470 

1.8456 

1.8393 
1.8323 

1.8308 

1.8258 
1.8198 

1.8184 



426 



STEAM 



Table 62. Properties of Saturated Steam. — Cont. 



Pressure 


Temp., 


Vol- 
ume, 
cu. ft. 
per lb. 


Weight, 
lb. per 
cu. ft. 


; Heat content 
in B.t.u. 


Latent 




Entropy 


1 

In. of 
mer- 
cury 


Lb, per 
sq. in. 
(Abs.) 


of 
liquid 


of 

vapor 


heatof 
vapori- 
zation o{ 

B.Tu. , ^^"^^ 


1 of va- 
poriza- 
tdon 


of 
vapor 




p ! t 


V 


1 

V 


q 


H 


1 ! ^ 


<t> 


14.92 


7.37 


179.14 51.14 


0.01955 


147.0 


1138.8 


991.7 


0.2617 1.5526 


1.8143 


13.92 


7.86 


182.06 48.14 


.02077 


149.9 


1140.0 


990.0 


.26621.5429 


1 
1.8091 


13.63 


8 


182.87 47.35 


0.02112 


150.8 


1140.3 


989.5 


0.26751.5402 

1 


1.8077 


12.92 


8.35 


184.83 45.49 


0.02198 


152.7 


1141.1 


988.3 


0.2705 


1.5337 


1.80i2 


11.92 


8.84 


187.46 


43.12 


.02319 


155.4 


1142.1 


986.7 


.2746 


1.5250 


1.7996 


11.60 


9 


188.28 


42.41 


0.02358 


156.2 


1142.5 


986.3 


0.2759 


1.5223 


1.7982 


10.92 


9.33 


189.97 40.99 


0.02439 


157.9 


1143.1 


985.2 


0.2785 


1.5168 


1.7953 


9.92 


9.82 


192.38 


39.08 


.02559 


160.3 


1144.1 


983.8 


.2822 


1.5089 


1.7912 


9.56 


10 


193.21 


38.43 


0.02602 


161.1 


1144.4 


983.3 


0.2835 


1.5062 


1.7897 


8.92 


10.31 


194.68 


37.34 


0.02678 


162.6 


1145.0 


982.4 


0.2858 


1.5015 


1.7873 


7.92 


10.81 


196.89 


35.75 


.02797 


164.8 


1145.9 


981.1 


.2892 


1.4944 


1.7835 


7.52 


11 


197.75 


35.16 


0.02844 


165.7 


1146.2 


980.5 


0.2905 


1.4916 


1.7821 


6.92 


11.30 


199.03 34.29 


0.02916 


167.0 


1146.7 


979.8 


0.2924 


1.4876 


1.7800 


5.92 


11.79 


201.09 


32.95 


.03035 


169.0 


1147.5 


978.5 


.2955 


1.4810 


1.7766 


5.49 


12 


201.96 


32.41 


0.03086 


169.9 


1147.9 


978.0 


0.2969 


1.4783 


1.7752 


4.92 


12.28 


203.08 31.71 


0.03153 


170.1 


1148.3 


977.3 


0.2986 


1.4747 


1.7733 


3.92 


12.77 


205.00 30.57 


.03271 


173.0 


1149.1 


976.1 


.3015 


1.4687 


1.7702 


3.45 


13 


205.88 30.07 


0.03326 


173.8 


1149.4 


975.6 


0.3028 


1.4659 


1.7687 


2.92 


13.26 


206.87 29.51 


0.03388 


174.8 


1149.8 


974.9 


0.3Oi3 


1.4629 


1.7671 


1.92 


13.75 


208.67 28.53 


.03505 


176.6 


1150.5 


973.8 


.3070 


1.4572 


1.7642 


1.42 


14 


209.56 28.06 


0.03564 


177.5 


1150.8 


973.3 


0.3083i 


1.4545 


1.7628 


0.92 


14.24 


210.43' 27.61 


0.03622 


178.4 


1151.2 


972.7 


0.3096 


1.4518 


1.7614 


0.0 


14.697 


212 26.81 


0.03730 


180.0 


1151.7 


971.7 


0.3120 


1.4469 


1.7589 


— 


14.74 212.13 26.75 


0.03739 


180.1 


1151.8 


971.7 


0.3122 


1.4465 


1.7587 



STEAM 



427 



Table 62. Properties of Saturated Steam. — Cont. 



Pressure 
Lb. per sq. in. 




Vol- 


Weight, 


Heat content 
in B.t.u. 


Latent 
heat of 


Entropy 






1 












Temp., 


ume, 


lb. per 






vapori- 










Absol- 
ute 


°F. 


cu. ft. 


cu. ft. 


of 


of 


zation 


of 


of va- 


of 


Gage 




per lb. 




liquid 


vapor 


in 
B.t.u. 


liquid 


poriza- 
tion 


vapor 




P 


t 


V 


1 

V 


q 


H 


L 


Cjjg 


L 
T 


45 


0.3 


15 


213.0 


26.30 


0.03802 


181.0 


1152.2 


971.2 


0.3135 


1.4438 


1.7573 


5.3 


20 


228.0 


20.10 


0.0498 


196.0 


1157.7 


961.7 


0.3356 


1.3987 


1.7343 


10.3 


25 


240.1 


16.32 


0.0613 


208.2 


1162.1 


953.8 


0.3531 


1.3633 


1.7164 


15.3 


30 


250.3 


13.76 


0.0727 


218.6 


1165.7 


947.1 


0.3679 


1.3340 


1.7019 


20.3 


35 


259.3 


11.91 


0.0840 


227.7 


1168.7 


941.0 


0.3805 


1.3090 


1.6895 


25.3 


40 


267.2 


10.51 


0.0951 


235.8 


1171.3 


935.5 


0.3917 


1.2871 


1.6788 


30.3 


45 


274.4 


9.41 


0.1062 


243.1 


1173.6 


930.5 


0.4017 


1.2677 


1.6694 


35.3 


50 


281.0 


8.53 


0.1173 


249.8 


1175.6 


925.9 


0.4108 


1.2501 


1.6609 


40.3 


55 


287.1 


7.80 


0.1283 


255.9 


1177.5 


921.5 


0.4190 


1.2342 


1.6532 


45.3 


60 


292.7 


7.18 


0.1392 


261.7 


1179.1 


917.4 


0.4267 


1.2195 


1.6462 


50.3 


65 


298.0 


6.66 


0.1501 


267.1 


1180.6 


913.5 


0.4338 


1.2058 


1.6397 


55.3 


70 


302.9 


6.22 


0.1609 


272.2 


1182.0 


909.8 


0.4405 


1.1931 


1.6336 


60.3 


75 


307.6 


5.82 


0.1717 


277.0 


1183.3 


906.2 


0.4468 


1.1812 


1.6280 


65.3 


80 


312.0 


5.48 


0.1824 


281.6 


1184.4 


902.8 


0.4527 


1.1700 


1.6227 


70.3 


85 


316.3 


5.18 


0.1932 


286.0 


1185.5 


899.6 


0.4583 


1.1595 


1.6178 


75.3 


90 


320.3 


4.905 


0.2039 


290.1 


1186.5 


896.4 


0.4636 


1.1495 


1.6131 


80.3 


95 


324.1 


4.663 


0.2145 


294.1 


1187.5 


893.4 


0.4687 


1.1400 


1.6087 


85.3 


100 


327.8 


4.442 


0.2251 


297.9 


1188.4 


890.5 


0.4736 


1.1309 


1.6045 


90.3 


105 


331.4 


4.240 


0.2358 


301.6 


1189.2 


887.6 


0.4782 


1.1222 


1.6004 


95.3 


110 


334.8 


4.057 


0.2465 


305.1 


1190.0 


884.8 


0.4827 


1.1138 


1.5965 


100.3 


115 


338.1 


3.889 


0.2572 


308.6 


1190.7 


882.1 


0.4870 


1.1058 


1.5928 


105.3 


120 


341.3 


3.735 


0.2678 


311.9 


1191.4 


879.5 


0.4911 


1.0982 


1.5893 


110.3 


125 


344.4 


3.593 


0.2783 


315.1 


1192.0 


876.9 


0.4950 


1.0908 


1.5858 


115.3 


130 


347.4 


3.461 


0.2889 


318.2 


1192.6 


874.4 


0.4989 


1.0836 


1.5825 


120.3 


135 


350.3 


3.340 


0.2994 


321.2 


1193.2 


872.0 


0.5026 


1.0767 


1.5793 


125.3 


140 


353.1 


3.226 


0.3100 


324.2 


1193.7 


869.6 


0.5062 


1.0700 


1.5762 


130.3 


145 


355.8 


3.120 


0.3206 


327.0 


1194.2 


867.2 


0.5097 


1.0636 


1.5733 


135.3 


150 


358.5 


3.020 


0.3311 


329.8 


1194.7 


864.9 


0.5131 


1.0573 


1.5704 


140.3 


155 


361.1 


2.927 


0.3417 


332.5 


1195.2 


862.7 


0.5164 


1.0512 


1.5676 


145.3 


160 


363.6 


2.839 


0.3522 


335.2 


1195.7 


860.5 


0.5196 


1.0453 


1.5649 


150.3 


165 


366.1 


2.757 


0.3627 


337.8 


1196.1 


858.3 


0.5227 


1.0395 


1.5622 


155.3 


170 


368.5 


2.679 


0.3733 


340.3 


1196.5 


856.2 


0.5258 


1.0339 


1.5597 


160.3 


175 


370.8 


2.605 


0.3838 


342.8 


1196.9 


854.1 


0.5287 


1.0284 


1.5572 


165.3 


180 


373.1 


2.536 


0.3943 


345.2 


1197.2 


852.0 


0.5316 


1.0231 


1.5547 


170.3 


185 


375.4 


2.470 


0.4048 


347.6 


1197.6 


849.9 


0.5344 


1.0179 


1.5523 



428 



STEAM 



Table 62. Properties of Saturated Steam. — Cont. 



Pressiire 








Heat content 






Lb. per s 


,q. in. 


Temp., 


Vol- 
ume, 


Weight, 

lb. per 


inB 


t.u. 


Latent 
heat of 
vapori- 


Entropy 












Gage 


Also- 
late 


=F. 


cu. ft. 
per lb. 


cu. ft. 


of 
liquid 


of 
vapor 


zation 

in 
B.t.u. 


of 
liquid 


of va- 
poriza- 
tion 


of 
vapor 




P 


t 


V 


1 


q 


H L 


T 


175.3 


190 


377.6 


2.408 


0.4154 


350 


1197.9 847.9 0.5372 


1.0128 1.5500 


180.3 


195 


379.7 


2.348 


0.4259 


352.2 


1198.2 846.0 0.5399 


1.0079 1.5478 


185.3 


200 


381.9 


2.292 


04304 


354.5 


1198.5 


S44.0 05426 


1.0030 1.5456 


1&0.3 


205 


383.9 


2.238 


0.4469 


356.7 


1198.7 


&42.1 05451 


0.9983 


1.5434 


195.3 


210 


386.0 


2.186 


0.457 


358.8 


1199.0 


8402 0.5477 


09936 


1.5413 


200.3 


215 


388.0 


2.137 


0.468 


361.0 


1199.2 


S38.3 0.5502 


0.9890 


1.5392 


205.3 


220 


390.0 


2.090 


0.478 


363.0 


1199.5 


836.5 0.5526 


0.9846 


1.5372 


210.3 


225 


391.9 


2.045 


0.489 


365.1 


1199.7 834.6 O5550 


0.9802 


1.5352 


215.3 


230 


393.8 


2.002 


0.499 


367.1 


1199.9 832.8 


0.5573 


0.9760 


1.5333 


220.3 


235 


395.6 


1.961 


O510 


369.1 


1200.1831.0 


0.5597 


09717 


1.5314 


225.3 


240 


397.5 


1.921 


0.521 


371.0 


1200.3 


829.3 


05619 


0.9676 


1.5295 


230.3 


245 


399.3 


1.883 


0531 


373.0 


1200.5 


827.5 


05041 


09635 


1.5276 


235.3 


250 


•iOl.l 


1.846 


0542 


374.9 


1200.6 


825.8 


05663 


0.9595 


1.5258 


240.3 


255 


402.9 


1.811 


0.552 


376.7 


1200.8 


824.1 


0.5685 


0.9556 


1.5241 


245.3 


260 


404.5 


1.777 


0.56.3 


378.6 


1201.0 


822.4 


0.5706 


09517 


1.5223 


250.3 


265 


406.2 


1.745 


0.573 


380.4 


1201.1 


8207 0.5727 


0.O479 


1.5206 


255.3 


270 


407.9 


1.713 


0.584 


382.2 


1201.2 


819.1 


0.5747 


0.9442 


1.5189 


260.3 


275 


409.6 


1.683 


0.594 


383.9 


1201.4 


817.4 


0.5(6. 


0.9405 


1.5172 


265.3 


280 


411.2 


1.654 


0.605 


3S5.7 


1201.5 


815.8 


0.5787 


09369 1.5156 


270.3 


285 


412.8 


1.625 


0.615 


387.4 


1201.6 


814.2 


O5806 


09333 1.5139 


275.3 


290 


414.4 


1.598 


0.626 


.389.1 


1201.7 


812.6 


0.5826 


09298 1.5123 


280.3 


295 


415.9 


1.571 


0636 


.390.8 


1201.8 


811.0 


05845 


09263 1.5108 


285.3 


300 


417.5 


1.545 


0047 


392.4 


1201.9 


809.4 


05863 


0.9229 


1.5092 


290.3 


305 


419.0 


1.520 


0.658 


394.1 


1202.0 


807.9 


0.5882 


09195 


1.5077 


295.3 


310 


420.5 


1.496 


0668 


395.7 


1202.0 


806.4 


0.5900 


0.91&2 


1.5062 


300.3 


315 


421.0 


1.473 


0.679 


397.3 


1202.1 


804.8 


0.5918 


09129 


1.5047 


305.3 


320 


423.4 


1.450 


0.690 


398.9 


1202.2 


803.3 


0.5935 


O9097 


1.5032 


310.3 


325 


424.9 


1.428 


O700 


400.4 


1202.2 


801.8 


05953 


0.9065 


1.5018 


315.3 


330 


426.3 


1.407 


0711 


402.0 


1202.3 


800.3 


O5970 


O9034 


1.50O4 


320.3 


335 


427.7 


1.386 


0721 


403.5 


1202.3 


798.9 


0.5987 


O9003 


1.4990 


325.3 


340 


429.1 


1.366 


0732 


405.0 


1202.4 


797.4 


O6004 


0.8972 


1.4976 


330.3 


345 


430.5 


1.346 


0.743 


406.5 


1202.4 


795.9 


0.6020 


0.8942 


1.4962 


335.3 


350 


431.9 


1.327 


0.753 


408.0 


1202.5 794.5 


06036 


08912 


1.4949 


360.3 


375 


438.5 


1.239 


0.807 


415.1 


1202.6 787.5 0.6115 


0.8768 


1.48^ 


385.3 


400 


444.8 


1.162 


0.860 


422.0 


1202.5 7806 O6190 


0.8631 


1.4821 



Table 63. Properties of Superheated Steam. 



429 



p* 


100 [327.8] 


105 [331.4] 


110 [334.8] 


115 [338.1] 


°F. 


V 


4) 


H 


V 


* 


H 


V 





H 


V 


4) 


H 


Sat. 


4.44 


1.6045 


1188.4 


4.24 


1.6004 


1189.2 


4.06 


1.5965 


1190.0 


3.89 


1.5928 


1190.7 


340 


4.53 


1.6130 


1195.2 


4.30 


1.6065 


1194.1 


4.09 


1.6002 


1192.9 


3.90 


1.5941 


1191.8 


350 

360 
370 
380 
390 


4.60 
4.67 
4.74 
4.81 
4.88 


1.6199 
1.6267 
1.6333 
1.6398 
1.6461 


1200.8 
1206.3 
1211.7 
1217.1 
1222.5 


4.37 
4.44 
4.50 
4.57 
4.64 


1.6135 
1.6203 
1.6270 
1.6335 
1.6399 


1199.7 
1205.3 
1210.8 
1216.2 
1221.6 


4.16 
4.22 
4.29 
4.35 
4.42 


1.6073 
1.6142 
1.6209 
1.6275 
1.6339 


1198.6 
1204.2 
1209.8 
1215.3 
1220.7 


3.97 
4.03 
4.09 
4.15 
4.21 


1.6012 
1.6082 
1.6150 
1.6217 
1.6282 


1197.5 
1203.2 

1208.8 
1214.3 
1219.8 


4eo 

410 
420 
430 
440 


4.95 
5.02 
5.08 
5.15 
5.22 


1.6523 
1.6585 
1.6645 
1.6704 
1.6762 


1227.8 
1233.1 
1238.4 
1243.6 

1248.8 


4.70 

4.77 
4.83 
4.90 
4.96 


1.6462 
1.6523 
1.6584 
1.6644 
1.6702 


1227.0 
1232.3 
1237.6 
1242.9 
1248.1 


4.48 
4.54 
4.60 
4.67 
4.73 


1.6403 
1.6465 
1.6526 
1.6586 
1.6645 


1226.1 
1231.5 
1236.9 
1242.2 
1247.4 


4.27 
4.34 
4.40 
4.46 
4.52 


1.6346 
1.6408 
1.6470 
1.6530 
1.6589 


1225.3 
1230.7 
1236.1 
1241.4 
1246.7 


450 

460 
470 
480 
490 


5.28 
5.35 
5.41 
5.48 
5.54 


1.6820 
1.6876 
1.6932 
1.6986 
1.7040 


1254.0 
1259.2 
1264.3 
1269.4 
1274.5 


5.02 
5.09 
5.15 
5.21 
5.27 


1.6760 
1.6817 
1.6872 
1.6927 
1.6981 


1253.3 
1258.5 
1263.7 
1268.8 
1273.9 


4.79 
4.85 
4.91 
4.97 
5.03 


1.6703 
1.6760 
1.6816 
1.6871 
1.6925 


1252.7 
1257.9 
1263.1 
1268.2 
1273.4 


4.57 
4.63 
4.69 
4.75 
4.80 


1.6647 
1.6704 
1.6761 
1.6817 
1.6871 


1252.0 

1257.2 
1262.4 
1267.6 
1272.8 


500 

550 
600 
650 
700 


5.61 
5.93 
6.24 
6.55 
6.86 


1.7093 
1.7349 
1.7592 

1.7822 
1.8042 


1279.6 
1304.8 
1329.8 
1354.8 
1379.7 


5.33 
5.64 
5.94 
6.24 
6.53 


1.7035 
1.7292 
1.7535 
1.7766 
1.7986 


1279.0 
1304.4 
1329.5 
1354.5 
1379.5 


5.09 
5.38 
5.67 
5.95 
6.23 


1.6979 
1.7237 
1.7481 
1.7712 
1.7933 


1278.5 
1303.9 
1329.1 
1354.2 
1379.2 


4.86 
5.14 
5.42 
5.69 
5.96 


1.6925 
1.7184 
1.7429 
1.7661 

1.7882 


1278.0 
1303.5 
1328.8 
1353.9 
1379.0 


750 


7.17 


1.8253 


1404.7 


6.82 


1.8197 


1404.5 


6.51 


1.8145 


1404.3 


6.23 


1.8094 


1404.1 



P* 


120 [341.3] 


125 [344.4] 


130 [347.4] 


135 [350.3] 


"F. 


V 


<t> 


H 


V 


* 


H 


V 


43 H 


V 


4> 


H 


Sat. 


3.74 


1.5893 


1191.4 


3.59 


1.5858 


1192.0 


3.46 


1.5825 


1192.6 


3.34 


1.5793 


1193.2 


350 


3.79 


1.5955 


1196.4 


3.63 


1.5899 


1195.3 


3.48 


1.5844 


1194.2 


3.39 


1.5863 


1198.9 


360 


3.85 


1.6025 


1202.1 


3.69 


1.5970 


1201.1 


3.54 


1.5916 


1200.0 


3.45 


1.5934 


1204.8 


370 


3.91 


1.6094 


1207.8 


3.75 


1.6039 


1206.8 


3.59 


1.5986 


1205.8 


3.50 


1.6003 


1210.5 


380 


3.97 


1.6161 


1213.4 


3.80 


1.6106 


1212.4 


3.65 


1.6054 


1211.5 


3.56 


1.6070 


1216.2 


390 


4.03 


1.6226 


1218.9 


3.86 


1.6172 


1218.0 


3.70 


1.6121 


1217.1 


3.61 


1.6136 


1221.8 


400 


4.09 


1.6291 


1224.4 


3.92 


1.6237 


1223.6 


3.76 


1.6186 


1222.7 


3.66 


1.6200 


1227.4 


410 


4.15 


1.6354 


1229.9 


3.97 


1.6301 


1229.1 


3.81 


1.6250 


1228.2 


3.72 


1.6263 


1232.9 


420 


4.21 


1.6415 


1235.3 


4.03 


1.6363 


1234.5 


3.87 


1.6313 


1233.7 


3.77 


1.6325 


1238.4 


430 


4.26 


1.6476 


1240.7 


4.08 


1.6424 


1239.9 


3.92 


1.6374 


1239.1 


3.82 


1.6386 


1243.8 


440 


4.32 


1.6536 


1246.0 


4.14 


1.6484 


1245.3 


3.97 


1.6434 


1244.5 


3.87 


1.6446 


1249.2 


450 


4.38 


1.6594 


1251.3 


4.19 


1.6543 


1250.6 


4.03 


1.6494 


1249.9 


3.92 


1.6505 


1254.6 


460 


4.43 


1.6652 


1256.6 


4.25 


1.6601 


1255.9 


4.08 


1.6552 


1255.2 


3.97 


1.6562 


1259.9 


470 


4.49 


1.6709 


1261.8 


4.30 


1.6658 


1261.2 


4.13 


1.6610 


1260.5 


4.02 


1.6619 


1265.2 


480 


4.54 


1.6765 


1267.0 


4.35 


1.6714 


1266.4 


4.18 


1.6666 


1265.8 


4.07 


1.6675 


1270.5 


490 


4.60 


1.6820 


1272.2 


4.41 


1.6770 


1271.7 


4.23 


1.6721 


1271.1 


4.12 


1.6730 


1275.7 


500 


4.65 


1.6874 


1277.4 


4.46 


1.6824 


1276.9 


4.28 


1.6776 


1276.3 


4.17 


1.6784 


1280.9 


510 


4.71 


1.6927 


1282.6 


4.51 


1.6878 


1282.0 


4.34 


1.6830 


1281.5 


4.22 


1.6837 


1286.2 


520 


4.76 


1.6980 


1287.7 


4.56 


1.6931 


1287.2 


4.39 


1.6883 


1286.7 


4.27 


1.6890 


1291.4 


530 


4.82 


1.7032 


1292.8 


4.62 


1.6983 


1292.4 


4.44 


1.6936 


1291.9 


4.32 


1.6942 


1296.6 


540 


4.87 


1.7083 


1297.9 


4.67 


1.7034 


1297.5 


4.49 


1.6987 


1297.0 


4.37 


1.6993 


1301.7 


550 


4.92 


1.7134 


1303.0 


4.72 


1.7085 


1302.6 


4.54 


1.7039 


1302.1 


4.60 


1.7241 


1327.3 


600 


5.19 


1.7379 


1328.4 


4.98 


1.7332 


1328.0 


4.78 


1.7285 


1327.7 


4.84 


1.7475 


1352.7 


650 


5.45 


1.7612 


1353.6 


5.23 


1.7565 


1353.3 


5.03 


1.7519 


1353.0 


5.07 


1.7698 


1378.0 


700 


5.71 


1.7833 


1378.7 


5.48 


1.7787 


1378.5 


5.27 


1.7742 


1378.2 


5.30 


1.7912 


1403.3 


750 


5.97 


1.8046 


1403.9 


5.73 


1.8000 


1403.7 


5.51 


1.7955 


1403.5 


5.53 


1.8117 


1428.7 



* To the right of (P) appear steam pressures and corresponding saturated steam 
temperatures; the latter are in bracltets. 

P and V are respectively the absolute pressure and the volume in cb. ft. per lb. ; and 
4> and H are the entropy and total heat of superheated steam measured from 32 deg. 



430 



Table 63. Properties of Superheated Steam — -Cont. 



p* 


140 :353 


1] 


145 [355 


•S] 


1 


50 [358 


■5] 


1 


55 [361 


11 


^F. 


cS 


H 


V 


O 


H 


V O 


H 


V e> 


H 


Sat. 


3.23| 1.5762 


ii;^3.7 


3.12 


1.5733 


1194.2. 


3.02 


1.5704 


1194.7 


2.93 


1.5676 


1195.2 


360 


3.26 1.5S13 
3.32 1.5SS4 


1197.9 
1203.7 


3.14 
3.19 


1.5763 
1.5S35 


1196.S 
1202.7 


3.03 
3. OS 


1.5715 
1.57S7 


1195.7 
1201.6 








370 


2.97 


1.5741 


1200.6 


3.S0 


3.37 1.5953 


1209.5 


3.25 


1.5905 


120S.5 


3.13 


1.5S5S 


1207.5 


3.02 


1.5812 


1206.5 


390 


3.42 


1.6021 


1215.2 


3.30 


1.59.3 


1214.3j 


3. IS 


1.5927 


1213.3 


3.07 


1.5881 


1212.4 


400 


3.4S 


1.60S7 


1220.9 


3.35 


1.6040 


1220.0 


3.23 


1.5994 


1219.1 


3.12 


1.5949 


1218.2 


410 


3.53 


1.6152 


1226.5 


3.40 


1.6106 


1225.7 


3.2S 


1.6060 


1224.8 


3.16 


1.6016 


1223.9 


420 


3.5S 1.6216 1232.1 


3.45 


1.6170 


1231.3 


3.33 


1.6124 


1230.4 


3.21 


1.60S1 


1229.6 


430 


3.63 1.627S 


1237.6 


3.50 1.6232 


1236. S 


3.37 


1.61SS 


1236.0 


3.26 1.6144 


1235.3 


440 


3.6S 


1.6339 


1243.1 


3.54 1.6294 


1242.3 


3.42 


1.6250 


1241.6 

1 


3.30 1.6207 


1240.8 


450 


3.73 


1.6400 


124S.5 


3.59 


1.6354 


1247.8 


3.4711.6310 


1247.1 


3.35 1.626S 


1246.3 


460 


3.7S 


1.645S 


1253.9 


3.64 


1.6414 


1253.2 


3.51 1.6370 


1252.5 


3.40 1.632S 


1251.8 


470 


3. S3 


1.6517 


1259.3 


3.69 


1.6472 


125S.6 


3.56 1.6429 


1257.9 


3.44 1.63S7 


1257.3 


4S0 


3.S7 


1.6573 


1264.6 


3.73 


1.6529 1264.0 


3.61 


1.64S6 


1263.3 


3.4S 1.6445 


1262.7 


490 


3.92 


1.6629 1269.9 

1 


3.7S 


1.65S6 


1269.3, 


3.65 


1.6543 


126S.7 


3.53 1.6502 

1 


1268.1 


500 


3.97 


1.66S5 1275.2 


3.S3 


1.6641 


1274.6 


3.69 


1.6599 


1274.0 


1 
3.57 1.655S 


1273.4 


510 


4.02 


1.6739 12S0.4 


3.S7 


1.6696 


1279.9 


3.74 


1.6654 


1279.3 


3.62 1.6613 


1278.8 


520 


4.06 


1.6793 12S5.6 


3.92 


1.6750 12S5.1 


3.7S 


1.670S 


12S4.6: 


3.66 1.6667 


1284.1 


530 


4.11 


1.6S46 1290.9 


3.97 


1.6S03 


1290.4 


3. S3 


1.6761 


12S9.9 


3.7011.6721 


12S9.3 


540 


4.16 


1.6S9S 1296.0 

1 1 


4.01 


1.6S55 


1295.6 


3.S7 


1.6S14 


1295.1 


3.75:1.6774 


1294.6 


550 


4.21 


1.6949 1301.2 


4.06 


1.6907 


1300.S 


3.92 


1.6S66 


1300.3 


3.79' 1.6826 


1299.8 


600 


4.44 


1.719S 1326.9 


4.2S 


1.7156 


1326.5 


4.13 


1 7116 


1326.1 


4.00 1.7077 


1325.8 


650 


4.66 


1.7433 1352.4 


4.50 


1.7392 


1352.1 


4.35 


1.7352 


1351.7 


4.20 1.7313 


1351.4 


700 


4.89 


1.7656 137/ .7 


4.72 1.7616 


1377.5 


4.56 


1.7576 


1377.2 


4.41 1.753S 


1377.0 


750 


5.11 


1.7S70 1403.1 

1 


4.93 1.7S30 

1 


1402.9 


4.77 


1.7791 


1402.6 


4.61 1.7753 

1 


1402.4 



P* 


160 :S63.6: 


165 [366.1] 


170 :36S.5: 


175 [370.8] 


=F. 


* 


H 


n 


e> 


H 


V rt H 


Sat. 


2.84 1.5040 

j 


1195.7 


2.7C 1.5622 1196.1 

1 j 


2.6S 1.5597 

1 


1106.5 
1 


2.61 1.5572 1196.9 


370 


2.87 


1.5696 


1199.5 


2.7S 1.5651 119S.5 


2.69 1.560S 


1197.4' 


1 1 


380 


9 qo 


1.5767 


1205.5 


2.S2 1.5723 1204.5 


2.73 1.5681 


1203.5 


2.65 1.56391 1202.5 


390 


2.97 


1.583S 


1211.4 


2.S7 1.5794 
j 


1210.5 


2.78 


1.5752 


1209.5: 


2.69 


1.5711 


1208.5 


400 


3.01 


1.5906 


1217.3 


2.92 1.5863 


I2I6.4' 


2.82 


1.5821 


1215.4 


-^ 


1.5781 


1214.5 


410 


3.06 


1.5973 


1223.1 


2.96 1.5931 


1222 2 


2.87 


1.5889 


1221.3 


2.7S 


1.5849 


1220.4 


420 


3.11 


1.603S 


12-^S S 


3.00 1.5997 


122s. 


2.91 


1.5956 


1227.11 


2.82 


1.5916 


1226.3 


430 


3.15 


1.6102 


1234.5 


3.05 1.6061 


1233.7 


2.95 


1.6021 


1232.8! 


2.86 1.5981 


1232.0 


4^0 


3.20 


1.6165 


1240.1 

1 


3.09 1.6124 


1239.3 


3.00 


1.6084 


1238.5. 


2.91jl.6045 


1237.7 


450 


3.24 


1.6226 


1245.6 


1 
3.14 1.6186 


1244.9 


3.04 


1.6146 


1244.2' 


2.95 1.6108 


1243.4 


460 


3.2s 


1.62S7 


1251.1 


3.1s 1.6247 1250.5 


3.0s 


1.6207 


1249.8 


2.99 1.6169 


1249.0 


470 


3.33 


1.6346 


1256.6 


3.22 1.6306 


1256.0 


3.12 


1.6267 


1255.3 


3.03 1.6230 


1254.6 


480 


3.37 


1.6404 


1262.1 


3.26 1.6365 


1261.4 


3.16 


1.6326 


1260.8 


3.07 


1.6289 


1260.1 


490 


3.41 


1.6461 


1267.5 

1 


3.31 1.6422 

1 


1266.9 


3.20 


1.6384 


1266.3 


3.11 


1.6347 


1265.6 


500 


3.46 


1.6518 


1272.9 


3.35 1.6479 


1272.3 


3.24 


1.6441 


1271.7 


3.15 


1.6404 


1271.1 


510 


3.50 


1.6573 


127S.2; 


3.39 1.6535 


1277.6 


3.29 


1.6497 


1277.1 


3.19 


1.6460 


1276.5 


520 


3.54 


1.662S 


12S3.5' 


3.43 1.65S9 


1283. 


3.33 


1.6552 


12S2.5 


3.23 


1.6515 


1281.9 


530 


3.5S 


1.66S2 12SS.S 


3.47 1.6643 


1288.3 


3.37 


1.6606 


1287.8 


3.27 


1.6570 


1287.3 


540 


3.62 


1.6735 1294.1 

1 1 


3.51 1.6697 


1293.6 


3.41 


1.6660 


1293.1 


3.30 


1.6624 


1292.6 


550 


3.67 


1.6787 1299.3 


3.55 1.6749 


1298.9 


3.45 


1.6712 


1298.4 


3.34 


1.6676 


1297.9 


600 


3.87 


1.7039 1325.4 


3.75 1.7002 


1325.0 


3.64 


1.6966 


1324.6 


3.53 


1.6931 


1324.2 


650 


4.07 


1.7276 1351.1 


3.95 1.7240 


1350.8 


3.83 


1.7204 


1350.5 


3.72 


1.7170 


1350.1 


700 


4.27 


1.7501 1376.7 


4.14 1.7466 


1376.4 


4.02 


1.7431 


1376.2: 


3.90 


1.7397 


1375.9 


750 


4.47 


1.7717 1402.2 


4.33 1.76i2 


1402.0 


4.20 


1.7647 


1401.8 


4.08 


1.7613 


1401.5 


800 


4.66 


1.7924 


1427.7 


4.52 1.7^x9 


1427.6 


4.3S 


1.7854 


1427.4 


4.26 


1.7821 


1427.2 


850 


4.85 


1.8123 


1453.4 


4.70,1.S0SS 1453.2, 


4.56 


1.S054 


1453.1 


4.43 


1.S021 


1452.9 



* To the right of vP; appear steam pressures and corresponding saturated steam 
temperatures ; the latter are in brackets. 

P and V are respectively the absolute pressure and the volume in cb. ft. per lb. ; and 
<t> and H are the entropy and total heat of superheated steam measured from 32 deg. 







Tabl 


e 63. 


Properties of Superheated Steam — Cont. 




431 


p* 


180 [373.1] 


185 [375.4] 


190 [377.6] 


195 [379.7] 


°F. 


V 





H 


V 


<P 


H 


V 


* 


H 


V 


<t> 


H 


Sat. 


2.54 


1.5547 


1197.2 


2.47 


1.5523 


1197.6 


2.41 


1.5500 


1197.9 


2.35 


1.5478 


1198.2 


380 


2.57 
2.61 


1.5598 
1.5670 


1201.4 
1207.6 


2.49 
2.53 


1.5558 
1.5631 


1200.4 
1206.6 


2.42 
2.46 


1.5518 
1.5592 


1199.4 
1205.6 








390 


2.39 


1.5554 


1204.6 


400 

410 
420 
430 
440 


2.65 
2.70 
2.74 

2.78 
2.82 


1.5741 
1.5810 
1.5877 
1.5943 
1.6007 


1213.6 
1219.5 
1225.4 
1231.2 
1237.0 


2.57 
2.62 
2.66 
2.70 
2.74 


1.5702 
1.5771 
1.5839 
1.5905 
1.5970 


1212.6 
1218.6 
1224.5 
1230.4 
1236.2 


2.50 
2.54 
2.58 
2.62 
2.66 


1.5663 
1.5733 
1.5801 
1.5868 
1.5933 


1211.7 
1217.7 
1223.7 
1229.6 
1235.4 


2.43 
2.47 
2.51 
2.55 
2.59 


1.5626 
1.5696 
1.5765 
1.5832 
1.5897 


1210.7 
1216.8 
1222.8 
1228.7 
1234.6 


450 
460 
470 
480 
490 


2.86 
2.90 
2.94 
2.98 
3.02 


1.6070 
1.6132 
1.6192 
1.6252 
1.6310 


1242.7 
1248.3 
1253.9 
1259.5 
1265.0 


2.78 
2.82 
2.86 
2.90 
2.93 


1.6033 
1.6095 
1.6156 
1.6216 
1.6275 


1241.9 
1247.6 
1253.3 
1258.9 
1264.4 


2.70 
2.74 

2.78 
2.81 
2.85 


1.5997 
1.6059 
1.6121 
1.6181 
1.6240 


1241.2 
1246.9 
1252.6 
1258.2 
1263.8 


2.63 
2.66 
2.70 
2.74 

2.77 


1.5961 
1.6024 
1.6086 
1.6146 
1.6206 


1240.4 
1246.2 
1251.9 
1257.5 
1263.1 


500 
510 
520 
530 
540 


3.06 
3.10 
3.13 
3.17 
3.21 


1.6368 
1.6424 
1.6480 
1.6534 
1.6588 


1270.5 
1275.9 
1281.4 
1286.8 
1292.1 


2.97 
3.01 
3.04 
3.08 
3.12 


1.6332 
1.6389 
1.6445 
1.6500 
1.6554 


1269.9 
1275.4 
1280.8 
1286.2 
1291.6 


2.89 
2.93 
2.96 
3.00 
3.03 


1.6298 
1.6355 
1.6411 
1.6466 
1.6520 


1269.3 
1274.8 
1280.3 
1285.7 
1291.1 


2.81 
2.85 
2.88 
2.92 
2.95 


1.6264 
1.6321 
1.6377 
1.6433 
1.6487 


1268.7 
1274.2 
1279.7 
1285.2 
1290.6 


550 

600 
650 

700 
750 


3.25 
3.43 
3.61 
3.79 
3.96 


1.6641 
1.6896 
1.7136 
1.7364 
1.7581 


1297.4 
1323.8 
1349.8 
1375.6 
1401.3 


3.16 
3.34 
3.51 
3.68 
3.85 


1.6607 
1.6863 
1.7104 
1.7331 
1.7549 


1297.0 
1323.4 
1349.5 
1375.4 
1401.1 


3.07 
3.25 
3.42 
3.59 
3.75 


1.6574 
1.6830 
1.7072 
1.7300 
1.7518 


1296.5 
1323.0 
1349.1 
1375.1 
1400.9 


2.99 
3.02 
3.06 
3.09 
3.13 


1.6541 
1.6594 
1.6646 
1.6698 
1.6749 


1296.0 
1301.4 
1306.7 
1312.0 
1317.3 


800 
850 
900 


4.14 
4.31 
4.49 


1.7789 
1.7989 
1.8183 


1427.0 
1452.7 
1478.6 


4.02 
4.19 
4.36 


1.7757 
1.7958 
1.8152 


1426.8 
1452.6 
1478.5 


3.92 
4.08 
4.25 


1.7727 
1.7927 
1.8121 


1426.6 
1452.4 
1478.3 


3.16 
3.33 
3.49 


1.6799 
1.7041 
1.7269 


1322.6 
1348.8 
1374.8 



P* 


200 [381.9] 


205 [383.9] 


210 [386.0] 


215 [388.0] 


°F. 


V 


* 


H 


V 


* 


H 


V 


* 


H 


V 

2.14 


4> 


H 


Sat. 


2.29 


1.5456 


1198.5 


2.24 


1.5434 


1198.7 


2.19 


1.5413 


1199.0 


1.5392 


1199.2 


390 


2.32 


1.5516 


1203.6 


2.26 


1.5479 


1202.6 


2.20 


1.5443 


1201.6 


2.15 


1.5407 


1200.5 


400 


2.36 1.5589 


1209.8 


2.30 


1.5552 


1208.8 


2.24 


1.5517 


1207.9 


2.18 


1.5482 


1206.9 


410 


2.40 


1.5660 


1215.9 


2.34 


1.5624 


1215.0 


2.28 


1.5589 


1214.1 


2.22 


1.5554 


1213.1 


420 


2.44 


1.5729 


1221.9 


2.38 


1.5693 


1221.1 


2.32 


1.5659 


1220.2 


2.26 


1.5625 


1219.3 


430 


2.48 


1.5796 


1227.9 


2.42 


1.5761 


1227.1 


2.35 


1.5727 


1226.2 


2.29 


1.5694 


1225.4 


440 


2.52 


1.5862 


1233.8 


2.45 


1.5828 


1233.0 


2.39 


1.5794 


1232.2 


2.33 


1.5761 


1231.4 


450 


2.56 


1.5927 


1239.7 


2.49 


1.5893 


1238.9 


2.43 


1.5859 


1238.1 


2.36 


1.5827 


1237.4 


460 


2.59 


1.5990 


1245.5 


2.53 


1.5956 


1244.7 


2.46 


1.5923 


1244.0 


2.40 


1.5891 


1243.3 


470 


2.63 


1.6052 


1251.2 


2.56 


1.6019 


1250.5 


2.50 


1.5986 


1249.8 


2.43 


1.5954 


1249.1 


480 


2.67 


1.6113 


1256.9 


2.60 


1.6080 


1256.2 


2.53 


1.6047 


1255.5 


2.47 


1.6015 


1254.8 


490 


2.70 


1.6172 


1262.5 


2.63 


1.6140 


1261.8 


2.57 


1.6108 


1261.2 


2.50 


1.6076 


1260.5 


500 


2.74 


1.6231 


1268.1 


2.67 


1.6199 


1267.4 


2.60 


1.6167 


1266.9 


2.54 


1.6136 


1266.2 


510 


2.77 


1.6288 


1273.6 


2.70 


1.6256 


1273.0 


2.63 


1.6225 


1272.5 


2.57 


1.6194 


1271.9 


520 


2.81 


1.6345 


1279.1 


2.74 


1.6313 


1278.6 


2.67 


1.6282 


1278.0 


2.60 


1.6251 


1277.4 


530 


2.84 


1.6400 


1284.6 


2.77 


1.6369 


1284.1 


2.70 


1.6338 


1283.5 


2.64 


1.6307 


1283.0 


640 


2.88 


1.6455 


1290.1 


2.80 


1.6424 


1289.6 


2.73 


1.6393 


1289.0 


2.67 


1.6363 


1288.5 


550 


2.91 


1.6509 


1295.5 


2.84 


1.6478 


1295.0 


2.77 


1.6447 


1294.5 


2.70 


1.6417 


1294.0 


560 


2.95 


1.6562 


1300.9 


2.87 


1.6531 


1300.4 


2.80 


1.6501 


1299.9 


2.73 


1.6471 


1299.4 


570 


2.98 


1.6614 


1306.2 


2.90 


1.6584 


1305.8 


2.83 


1.6553 


1305.3 


2.76 


1.6524 


1304.9 


580 


3.01 


1.6666 


1311.6 


2.94 


1.6636 


1311.1 


2.86 


1.6605 


1310.7 


2.80 


1.6576 


1310.3 


590 


3.05 


1.6717 


1316.9 


2.97 


1.6687 


1316.5 


2.90 


1.6657 


1316.1 


2.83 


1.6628 


1315.6 


600 


3.08 


1.6768 


1322.2 


3.00 


1.6737 


1321.8 


2.93 


1.6707 


1321.4 


2.86 


1.6678 


1321.0 


650 


3.24 


1.7010 


1348.5 


3.16 


1.6981 


1348.2 


3.09 


1.6951 


1347.8 


3.01 


1.6923 


1347.5 


700 


3.40 


1.7239 


1374.5 


3.32 


1.7211 


1374.3 


3.24 


1.7182 


1374.0 


3.16 


1.7154 


1373.7 


750 


3.56 


1.7458 


1400.4 


3.48 


1.7429 


1400.2 


3.39 


1.7401 


1399.9 


3.31 


1.7374 


1399.7 



* To the right of (P) appear steam pressures and corresponding saturated steam 
temperatures; the latter are in brackets. 

P and V are respectively the absolute pressure and the volume in cb. ft. per lb. ; and 
<t> and H are the entropy and total heat of superheated steam measured from 32 deg. 



432 



Table 63. Properties of Superheated Steam — Cont. 



p* 


220 [390.0] 


' 225 [391.9] 


230 [393.8] 


' 235 [395.6] 


°F. 


V 


(t> 


H 


1 ^' 


<t> 


H 


V 





H 


1 V 


<t> 


n 


Sat. 


2.09 


1.5372 


1199.5 


2.05 


1.5352 


1199.7 


2.00 


1.5333 


1199.9 


1.96 


1.5314 


1200.1 


400 


2.13 


1.5447 


1205.9 


2.08 


1.5413 


1204.9 


2.02 


1.5379 


1204.0 


1.98 


1.5346 


1202.9 


410 


2.17 


1.5520 


1212.2 


2.11 


1.54S() 


1211.3 


2.06 


1.5453 


1210.3 


2.01 


1.5421 


1209.4 


420 


2.20 


1.5591 


1218.41 


2.15 


1.555S 


1217.5 


2.10 


1.5526 


1216.6 


2.05 


1.5494 


1215.7 


430 


2.24 


1.5660 


1224. o 


2.18 


1.5628 


1223.7 


2.13 


1.5596 


1222.8 


2.08 


1.5564 1222.0 


440 


2.27 


1.5728 


1230.6 


2.22 


1.5696 


1229.8 


2.16 


1.5664 


1229.0 


2.11 


1.5633 1228.2 


450 


2.31 


1.5794 


1236.6 


2.25 


1.5762 


1235.8 


2.20 


1.573l' 


1235.0 


2.15 


1.5700 1234.3 


4G0 


2.34 


1.5859 


1242.5, 


2.28 


1.5827 


1241.8 


2.23 


1.5797 


1241.0 


2.18 


1.5766 


1240.3 


470 


2.38 


1.5922 


1248.4 


2.32 


1.5891 


1247.7 


2.26 


1..5861 


1246.9 


2.21 


1..5831 


1246.2 


480 


3.41 


1.5984 


1254.2 


2.35 


1.5953 


1253.5 


2.30 


1.5923! 


1252.8 


2.24 


1.5894 


1252.1 


490 


2.44 


1.6045 


1259.9 


2.38 


1.6014 


1259.3 


2.33 


1.5985 


1258.6 


2.28 


1.5955 


1257.9 


500 


2.47 


1.6105 


1265.6 


2.42 


1.6074 


1265.0 


2.36 


1.6045 


1264.4 


2.31 


1.6016 


1263.7 


510 


2.51 


1.6163 


1271.3 


2.45 


1.6133 


1270.7 


2.39 


1.6104 


1270.1 


2.34 


1.6075 


1269.5 


520 


2.54 


1.6221 


1276.9 


2.48 


1.6191 


1276.3 


2.42 


1.6162i 


1275.7 


2.37 


1.6134 


1275.1 


530 


2.57 


1.6277 


1282.51 


2.51 


1.6248 


1281.9 


2.45 


1.62191 


1281.3 


2.40 


1.6191 


1280.8 


540 


2.60 


1.6333 


1288.0 


2.54 


1.6304 


1287.5 


2.49 


1.6275 


1286.9 


2.43 


1.6247 


1286.4 


550 


2.64 


1.6388 


1293.5 


2.57 


1.6359 


1293.0 


2.52 


1.6331 


1292.5 


2.46 


1.6303 


1292.0 


560 


2.67 


1.6442 


1299.0 


2.60 


1.6413 


1298.5 


2.55 


1.6385i 


1298.0 


2.49 


1.6357 


1297.5 


570 


2.70 


1.6495 


1304.4 


2.64 


1.6466 


1303.9 


2.58 


1.64381 


1303.5 


2.52 


1.6411 


1303.0 


580 


2.73 


1.6547 


1309.8 


2.67 


1.6519 


1309.4 


2.61 


1.649l| 


1308.9 


2.55 


1.6464 


1308.5 


590 


2.76 


1.659i; 


1315.2 


2.70 


1.6571 


1314.8 


2.64 


1.6543 


1314.3 


2.58 


1.6516 


1313.9 


600 


2.79 


1.6650 


1320.6 


2.73 


1.6622 


1320.2 


2.67 


1.6594 


1319.7 


2.61 


1.6567 


1319.3 


650 


2.94 


1.6895 


1347.1 


2.88; 


1.68GS 


1346. s; 


2.81 


1.6841 


1346.5 


2.75 


1.6815 


1346.1 


700 


3.09 


1.7126 


1373.4, 


3.02 


1.7100 


1373.11 


2.95 


1.7073 


1372.8 


2.89 


1.7047 


1372.5 


750 


3.24 


1.7346 


1399.5' 


3.16 


1.7320 


1399.2 


3.09 


1. 72941 


1399.0 


3.03 


1.7269 


1398.8 


800 


3.38 


1.7557 


1425.5! 


3.30 


1.7531 


1425.3 


3.23 


1.7505 


1425.1 


3.16 


1.7480 


1424.9 



P*l 


240 [397 


5] 


245 [399.3] , 


i 2 


50 [401.1] 


2 


55 [402.9] 


°F. 


V 


O 


n 


V 





H 


V 





n 


V 


<J> 


H 


Sat. 


1.92 


1.5295 


1200.3 


1.88 


1.5276 


1200.5 


1.846 


1.5258 


1200.6! 


1.811 


1.5241 


1200.8 


400 


1.93 


1.5314 


1202.0 






1 












410 


1.96 


1.5389 


1208.4 


1.92 


1.5357 


1207.5 !l.877 


1.5326 


1206.5 


1.835 


1.5295 


1205.6 


420 


2.00 


1.5462 


1214.8 


1.95 


1.5430 


1213.91 1.910 


1.5400 


1213.0 


1.868 


1.5369 


1212.1 


430 


2.03 


1.5533 


1221.1 


1.99 


1.5502 


1220.2 1.942 


1.5472 


1219.4 


1.900 


1.5442 


1218.5 


440 


2.07 


1.5602 1227.3 


2.02 


1.5572 


1226.5 


1.974 

1 


1.5542 


1225.7 


1.932 


1.5513 


1224.8 


450 


2.10 


1.567o!l233.5 


2.05 


1.5640 


1232.7 


2.006 


1.5611 


1231.91 


1.963 


1.5582 


1231.1 


460 


2.13 


1.5736 


1239.5 


2.08 


1.5707 


1238.8 


j2.038 


1.5678 


1238.0 '1.994 


1.5649 


1237.2 


470 


2.16 


1.5801 


1245.5 


2.11 


1.5772 


1244.8 


2.069 


1.5743 


1244.0 2.02.-) 


1.5715 


1243.3 


480 


2.19 


1.5864 


1251.4 


2.15 


1.5836 


1250.7 


12.099 


1.5807 


1250.0 2.055 


1.5779 


1249.3 


490 


2.23 


1.5926 


1257.3 


2.18 


1.5898 


1256.6 


2.129 


1.5870 


1255.9 


2.085 


1.5842 


1255.3 


500 


2.26 


1.5987 


1263.1 


2.21 


1.5959 


1262.5 


2.159 


1.5931 


1261.8 


2.114 


1.5904 


1261.2 


510 


2.29 


1.6047 


1268.8 


2.24 


1.6019 


1268.2 


2.189 


1.5991 


1267.61 


2.143 


1.5964 


1267.0 


520 


2.32 


1.6105 


1274.5 


2.27 


1.6078 


1274.0 


2.218 


1.6050 


1273.4' 


2.172 


1.6024 


1272.8 


530 


2.35 


1.6163 


1280.2 


2.30 


1.6135 


1279.7 


'2.247 


1.6108 


1279.1 


2.201 


1.6082 


1278.5 


540 


2.38 


1.6220 


1285.9 


2.33 


1.6192 


1285.3 


2.276 


1.6166 


1284.8 


2.229 


1.6139 


1284.2 


550 


2.41 


1.6275 


1291.4 


2.36 


1.6248 


1290.9 


2.305 


1.6222 


1290.4 


2.257 


1.6196 


1289.8 


560 


2.44 


1.6330 


1297.0 


2.38 


1.6303 


1296.5 2.333 


1.6277 


1296.0 


2.285 


1.6251 


1295.5 


570 


2.46 


1.6384 


1302.5 


2.41 


1.6357 


1302.0 2.361 


1.6331 


1301.6 


2.313 


1.6305 


1301.1 


580 


2.49 


1.6437 


1308.0 


2.44 


1.6410 


1307.5 2.389 


1.6384 


1307.1 


2.340 


1.6359 


1306.6 


590 


2.52 


1.6489 


1313.5 


2.47 


1.6463 


1313.0; 2.417 


1.6437 


1312.6, 


2.368 


1.6412 


1312.1 


600 


2.55 


1.6541 


1318.9 


2.50 


1.6514 


1318.5 2.444 


1.6489 


1318.1 


2.395 


1.6464 


1317.6 


650 


2.69 


1.6789 


1345.8 


2.63 


1.6763 


1345.4 2.579 


1.6738 


1345.1 


2.527 


1.6714 


1344.7 


700 


2.83 


1.7022 


1372.3 


2.77 


1.6997 


1372.0; 2.711 


1.6973 


1371.7 


2.657 


1.6949 


1371.4 


750 


2.96 


1.7244 


1398.5 


2.90 


1.7219 


1398.3! 2.840 


1.7195 


1398.0 


2.784 


1.7172 


1397.8 


800 


3.09 


1.7456 


1424.7 


3.03 


1.7431 


1424.5 .2.968 


1.7408 


1424.3, 


2.909 


1.7385 


1424.1 



• To the right of (P) appear steam pressures and corresponding saturated steam 
temperatures; the laiter are in brackets. 

P and V are respectively the absolute pressure and the volume in cb. ft. per lb.; and 
4> and H are the entropy and total heat of superheated steam measiured from 32 deg. 



Table 63. Properties of Superheated Steam — Cont. 



433 



260 [404.5] 



1.777 

1.795 

1.828 
1.860 
1.891 

1.922 
1.952 
1.982 
2.012 
2.042 

2.071 
2.099 
2.128 
2.156 
2.184 

2.212 
2.239 
2.266 
2.293 
2.320 

2.347 
2.477 
2.605 
2.730 
2.853 

2.974 



O 



1.5223 

1.5264 
1.5339 
1.5413 
1.5484 

1.5553 
1.5621 
1.5687 
1.5752 
1.5815 

1.5877 
1.5938 
1.5998 
1.6056 
1.6113 

1.6170 
1.6225 
1.6280 
1.6334 
1.6387 

1.6439 
1.6690 
1.6925 
1.7149 
1.7362 

1.7566 



H 



1201.0 

1204.6 
1211.2 
1217.6 
1224.0 

1230.3 
1236.5 
1242.6 
1248.6 
1254.6 

1260.5 
1266.4 
1272.2 
1278.0 
1283.7 

1289.4 
1295.0 
1300.6 
1306.2 
1311.7 

1317.2 
1344.4 
1371.1 
1397.6 
1423.8 

1450.1 



265 [406.2] 



1.745 

1.757 
1.789 
1 820 
1.851 

1.882 
1.912 
1.942 
1.971 
2.000 

2.029 
2.057 
2.085 
2.113 
2.140 

2.168 
2.195 
2.221 

2.248 
2.274 

2.301 
2.429 
2.555 

2.678 
2.798 

2.917 



H 



1.5206 

1.5234 
1.5309 
1.5383 
1.5455 

1.5525 
1.5593 
1.5659 
1.5724 

1.5788 

1.5850 
1.5911 
1.5971 
1.6030 
1.6088 

1.6145 
1.6200 
1.6255 
1.6309 
1.6362 

1.6415 
1.6666 
1.6902 
1.7126 
1.7339 

1.7544 



1201.1 

1203.6 
1210.2 
1216.7 
1223.1 

1229.5 
1235.7 
1241.8 
1247.9 
1253.9 

1259.9 
1256.8 
1271.6 
1277.4 
1283.1 

1288.8 
1294.5 
1300.1 
1305.7 
1311.2 

1316.7 
1344.0 
1370.8 
1397.3 
1423.6 

1449.9 



270 [407.9] 



1.713 



1.751 
1.782 
1.813 

1.843 
1.873 
1.902 
1.931 
1.960 

1.988 
2.016 
2.044 
2.071 
2.098 

2.125 
2.152 
2.178 
2.204 
2.230 

2.256 
2.382 
2.506 
2.627 
2.746 

2.863 



1.5189 



1.5281 
1.5355 
1.5427 

1.5497 
1.5565 
1.5632 
1.5698 
1.5762 

1.5824 
1.5885 
1.5946 
1.6005 
1.6063 

1.6120 
1.6176 
1.6231 
1.6285 
1.6338 

1.6391 
1.6643 
1.6879 
1.7104 
1.7317 

1.7522 



H 



1201.2 



1209.3 
1215.8 
1222.3 

1228.6 
1234.9 
1241.1 
1247.2 
1253.2 

1259.2 
1265.1 
1271.0 

1276.8 
1282.6 

1288.3 
1294.0 
1299.6 
1305.2 
1310.8 

1316.3 
1343.7 
1370.5 
1397.1 
1423.4 

1449.7 



275 [409.6] 



1.683 



1.715 
1.746 
1.776 

1.806 
1.835 
1.864 
1.893 
1.921 

1.949 
1.977 
2.004 
2.031 
2.058 

2.084 
2.110 
2.136 
2.162 
2.1: 

2.213 
2.338 
2.459 
2.578 
2.695 

2.810 



1.5172 



H 



1201.4 



1.5252 
1.5326 
1.5399 

1.5469 
1.5538 
1.5605 
1.5671 
1.5735 

1.5798 
1.5860 
1.5920 
1.5980 
1.6038 

1.6095 
1.6151 
1.6206 
1.6261 
1.6314 

1.6367 
1.6620 
1.6857 
1.7082 
1.7296 

1.7501 



1208.4 
1215.0 
1221.4 

1227.8 
1234.1 
1240.3 
1246.5 
1252.6 

1258.6 
1264.5 
1270.4 
1276.2 
1282.0 

1287.8 
1293.5 
1299.1 
1304.7 
1310.3 

1315.9 
1343.3 
1370.2 
1396.8 
1423.2 

1449.6 



280 [411.2] 



1.654 

1.680 
1.711 
1.741 

1.770 
1.799 
1.828 
1.856 

1.884 

1.911 
1.939 
1.966 
1.992 
2.019 

2.045 
2.070 
2.096 
2.122 
2.147 

2.172 
2.295 
2.414 
2.531 
2.646 

2.759 

2.872 



1.5156 

1.5223 
1.5298 
1.5371 

1.5442 
1.5511 
1.5579 
1.5645 
1.5710 

1.5773 
1.5835 
1.5895 
1.5955 
1.6013 

1.6071 
1.6127 
1.6182 
1.6237 
1.6291 

1.6344 
1.6597 
1.6835 
1.7060 
1.7274 

1.7480 
1.7677 



H 



1201.5 

1207.4 
1214.1 
1220.6 

1227.0 
1233.3 
1239.6 
1245.8 
1251.9 

1257.9 
1263.9 
1269.8 
1275.7 
1281.5 

1287.2 
1292.9 
1298.6 
1304.3 
1309.9 

1315.5 
1342.9 
1369.9 
1396.6 
1423.0 

1449.4 
1475.7 



285 [412.8] 



1.625 

1.647 
1.677 
1.707 

1.736 
1.764 
1.792 
1.820 

1.848 

1.875 
1.902 
1.929 
1.955 
1.981 

2.007 
2.032 
2.057 
2.082 
2.107 

2.132 
2.253 
2.371 
2.486 
2.599 

2.710 

2.821 







1.5139 

1.5195 
1.5270 
1.5344 

1.5415 
1.5485 
1.5553 
1.5619 
1.5684 

1.5748 
1.5810 
1.5871 
1.5931 
1.5989 

1.6047 
1.6103 
1.6159 
1.6214 
1.6268 

1.6321 
1.6575 
1.6813 
1.7039 
1.7253 

1.7459 
1.7657 



H 



1201.6 

1206.5 
1213.2 
1219.7 

1226.2 
1232.6 
1238.8 
1245.0 
1251.2 

1257.3 
1263.3 
1269.2 
1275.1 
1280.9 

1286.7 
1292.5 
1298.2 
1303.8 
1309.4 

1315.0 
1342.6 
1369.6 
1396.3 
1422.8 

1449.2 
1475.6 



290 [414.4] 



1.598 

1.614 
1.644 
1.673 



702 
730 
758 
786 
813 



1.840 
1.866 
1.893 
1.919 
1.944 

1.970 
1.995 
2.020 
2.045 
2.069 

2.093 
2.213 
2.329 
2.442 
2.553 

2.663 
2.772 



1.5123 

1.5167 
1.5243 
1.5317 

1.5389 
1.5459 
1.5527 
1.5594 
1.5659 

1 5723 
1.5785 
1.5846 
1.5906 
i;5965 

1.6023 
1.6080 
1.6136 
1.6191 
1.6245 

1.6298 
1.6553 
1.6792 
1.7018 
1.7233 

1.7439 
1.7637 



H 



1201.7 

1205.5 
1212.3 
1218.9 

1225.4 
1231.8 
1238.1 
1244.3 
1250.5 

1256.6 
1262.6 
1268.6 
1274.5 
1280.4 

1286.2 
1291.9 
1297.6 
1303.3 
1309.0 

1314.6 
1342.2 
1369.3 
1396.1 
1422.6 

1449.0 
1475.4 



295 [415.9] 



1.571 

1.583 
1.612 
1.641 

1.670 
1.698 
1.725 
1.753 
1.780 

1.806 
1.832 
1.858 
1.884 
1.909 

1.934 
1.959 
1.984 
2.008 
2.032 

2.056 
2.174 
2.288 
2.400 
2.509 

2.617 
2.724 



<t> 



1.5108 

1.5139 
1.5216 
1.5290 

1.5362 
1.5432 
1.5501 
1.5568 
1.5634 

1.5698 
1.5761 
1.5823 
1.5883 
1.5942 

1.6000 
1.6057 
1.6113 
1.6168 
1.6222 

1.6276 
1.6532 
1.6771 
1.6997 
1.7213 

1.7419 
1.7617 



H 



1201.8 

1204.6 
1211.4 
1218.0 

1224.5 
1231.0 
1237.3 
1243.6 
1249.8 

1255.9 
1262.0 
1268.0 
1273.9 
1279.8 

1285.6 
1291.4 
1297.1 
1302.8 
1308.5 

1314.1 
1341.8 
1369.0 
1395.8 
1422.4 

1448.9 
1475.3 



* To the right of (P) appear steam pressures and corresponding saturated steam 
temperatures; the latter are in brackets. 

P and V are respectively tlie absolute pressure and the volume in cb. ft. per lb. ; and 
4> and H are the entropy and total heat of superheated steam measured from 32 deg. 



434 



Table 63. ProDerties of Suoerheated Steam — Coni^, 



p* 


300 '417.5; 


310 ;420.5; 


320 :423.4; 330 :426.3: 


'Y . 


V c H 


T c H 


V 


- 


H - o H 


Sat. 


1.545 1.5092 1201.9 


1.496 


1.5062 1202.0J 


jl.4o0 


1.5032 


1202.2 1.407 


1.50Q4 


1202.3 


430 


1.5S2 1.51S9 1210.4 


1.523 


1.5136 120S.6 


1.469 


1.50S4 


1206. S 1.417 


1.5033 


1204.9 


440 


1.610 1.5263 1217.1 


1.551 


1.5211 1215.4 


1.496 


1.51 60 


1213.6 !l.444 
1 


1.5110 


1211.8 


450 


1.63S 1.5336 1223.7 


1.57:- 


, r^v^ 1222.0' 


1.523 


1.5235 


1220.3" 1.471 


1.51S6 


1218.6 


460 


1.666 1.54:07 1230.2 


1.60-; 


= - -- -1 -)o<; 5 


1.550 


1.5307 


1227.0 1.497 


1.5259 


1225.3 


470 


1.693 1..5476 1236.6 


l.oi-; 


1 :^-: 1235.0 


,1.576 


1.537S 


1233.5 1.522 


1.53:^ 


1231.9 


-Ivfl 


1.720 1.5544 1242 : 


■ '- .-. ■.< 


1 54^5 1241.4 


1.602 


1.5447 


1239.9 1.547 


1.5400 


123S.4 


4yO 


1.747 1.5610 124.^ 1 


- •: >o 


1.5561 1247.7 


1.627 


1.5514 


1246.3 1.572 


1.546S 


1244.9 


500 


1.773 1.5674 1255.2 


1.711 


1.5626 1253.9; 


; 1.652 


1.55S0 


1252.6 ,1-597 


1.5534 


1251.2 


510 


1.799 1.5737 1261.3 


1.736 


1.5690 1260.0 


1.677 


1.5644 


125S.8 


1.621 


1.5599 


1257.4 


520 


1.S25 1.5799 1267.4 


1.761 


1.5752 1266.1 


1.701 


1.5707 


1264.9 


1.6*5 


1.5662 


1263.6 


530 


1.V.50 1.5S.59 1273 3 


1.7S6 


1 5S13 1272.1 


1.725 


1.5. 6S 


1271.0 


1.669 


1.5724 


1269.7 


540 


1.S75 1.591V ::-;■ : 


- >- - 


: '>"! 127S.1 


1.749 


1.5S29 


1277.0 


1.692 


1.5785 


1275.8 


550 


-.-■:: 1.5977 12S.: L 


' -i : _ 


- - :.; _ 12^4 ' 


; 


- - V V ^ 


12S2 ':' 1 715 


1.5S45 


12S1.S 


560 


: -^ 1 60:34 12v; ! 


^ - V 


• -:.-,."'" V :. V 


1 " ;■ -; 


' - --:- 


l-^- > 1 73S 


1.5903 


12S7.7 


5. 


l.c-^- 1.6090 12.;-: 


^^_ 


" -,,\4.n 1295.'! 


i . ^l f 


1 . OVJO 


1294.';' i. 1 61 


1.5961 


1293.6 


ovO 


1.973 1.6146 130- ^ 


• ■ 


L ';.102 1301.4 


l.■^42 


1.6059 


1300.4 1.7S3 


1.6017 


1299.5 


590 


1.997 1.6200 130^1 


1.-2- 


1.6157 1307.1 


1.S65 


1.6114 


1306.2 1.S05 


1.6073 


1305.2 


600 


2.020 1.6254 1313.7' 


1 1.952 


1.6211 1312 S 


1.SS7 


1.6169 


1311.9 1.S27 1.612S 


1311.0 


650 


2.136 1.6510 134: ^ 


- ■T'O 


1.64r69 1340.7 


1 997 


1.642S 


1340.0 1.934 1.63SS 


1339.3 


700 


2.249 1.6750 13— ' 


- :"4 


1.6710 136S.1 


2.104 


1.6670 


1367.5 2.03S 1.6632 


1366.9 


7-"' ' 


2.359 1.6977 13vo : 


-._>i 


1.6937 1395.0 


2.20S 


]^ t^xQx 


1394. ." ■"' T sr, 1 Ai.Ai 


1394.0 


S !>' J 


2.467 1.7193 1422.2 


2.3S6 


1.7153 1421.7 


2.310 


1.7115 


1421 1 


_ _ ; ■ 


^ 


1420.9 



2 573 1.7399 144 
_ '57S 1.7597 147 



.7 2.4S9 1.736C> 144S.3 2.410 1.7323 1447.9 
.1 2.591 1.7559 1474. S 2.509 1.7522 1474. 5 



2.336 1.72 So 1447.6 
2.443 1.74S6 1474.2 



P* 



341:1 



360 434. 



3S0 '439. 



400 :444.S" 



- ^ I * I ^ i( ^ j * I ^ |j ^ ! * I 



Sat. 1.366 1.4976 1202.4 1.291 1.4922 



430 
440 

450 
460 
470 
4S0 
490 

5M 
510 
520 
530 
540 

539 
560 
570 
580 
590 

6§0 
650 
700 
750 2 
8«0 2 

850 2 

900 2 



36S 1.49S3 1203.0 
395 1.5061 1210.0j 

421 1.5137 12I6.9I 
447 1.5211 1223. 7I 
472 1.52-S3 1230.4; 
497 1.. 53.54 123- 



1.355 
1.379 

403 



1202.5 



1.223 1.4S71 1202.6, 



1.5119 1220.4 

1.5193 1227.2 
1.526.5 1233.9 



1.162 1.4821 1202.0 



521:1.5422 12^ : ^27 1.5335 1240. 5 



1.272 1.5030 1217.0 

1.296 1.5105 1224.0 
1.319 1.517S 1230.S 
1.342 1.5249 1237.5 



545 
569 
592 
615 
638 

661 
683 
705 
727 
7491 



770 1 



875 

976 



1..54> 1-^ 
1.555 : - - ' 

1.5619 12o2. 
1.56^1 126S. 
1.5743 1274 

1.5803 12 f 
1.5S62 1- 



1.450 1.5403 1 
1.473 1.5469 1 
1.495 1.5534 1 
1.51. 1.559S 1 
1 ?39 1.5660 1 

I 
1 -:1 1.5721 1 



247.0 
2.53.4 

2-59. S 
266.1 
272.3 



1.592: - 
1.5977 1_ 
1.6033 13 



1.364 
1.3S6 
1.40S 
1.429 
1.451 

1.472 
1.492 



1.5319 
1.5:3S7 
1.5453 
1.551> 

1.55S1 

1^5" ^4 
1.5"^^ 



1.533 

1.553 



1.5>-- 

1.5SS0 



1244.2 
1250.7 
1257.2 
126:3.6 
1269.9 

1276.1 
i:-2.3 

l_->.4 
i2i'4.4 
1:300.4 



1 . : ' . ; ; 

1.65.^4 lo: 
075 1.6S24 13: 
172 1.7042 14: 



. _>010'130>.2 

1 6275 1337.0 

3 1.6522 1365.0 

7 1.6754 1392.4 

:9 1.6974 1419.5 



1.572 1.5936 1306.4 
1.669 1.6204 1335.4 
1.761 1.6453 1363.7 
1.S51 1.66S7 1391.4 
1.939 1.690S 141S.6 



1.198 1.4943 1213.6 
1.221 1.5020 1220.7 
1.243 1.5094 1227.7 
1.265 1.5167 1234.6 

1.2S7'l.523S 1241.3 
1.309 1.5307 124S.0 
1.330 1.5374 1254.6 
1.350 1.5440 1261.1 
1.371 1.5505 1267.5 

1.391 1.556S 1273. S 

1.411 1.56- ::> 

1.430 1.56:- :_^ 2 
1.450 1.574;- i-r-_.4 
1.469 1.5S07 129S.5 

1.4S.S 1.5S64 1304.5 
1.5S1 1.6136 1333.9 
1.669 1.63S7 1362.4 
1.755 1.6622 1390.3 
1x3'^ 1 6S45 1417.7 



267 1.7251 1447 
360 1.7451 1473 



2.139 1.71S3 1446.5 2.024 1.711S 1445.7 1 : - 1 1 .J-b. 1444.9 
2 22^ 1.73S4 1473.3 2.109 1.7320 1472.6 2.002 1.7259 1472.0 



* To the right of P appear steam pressures and corresponding saturated steaxn 
temperatures: the latter are in brackets. 

P and V are respectivelv the absolute pressure and the volume in cb. ft. i>er lb. : and 
4> and H are the entropy and total heat of superheated steam measured from 32 deg. 



435 



Chapter 13 



FUEL 

COAL in its different forms is the principal fuel used in boilers. Its appli- 
cation, anal3^sis and purchase have been most highly developed. The 
use of oil is increasing rapidly, and other fuels are employed when 
factors of economy or delivery warrant. Natural gas and crude oil or 
petroleum have the highest heat value of the commercial gaseous and liquid 
fuels ; and because of their ease of operation, gas and oil are highly regarded 
as fuels. 

Classification of Coals 

COAL is a dark brown or black mineral substance, found in the carbonif- 
erous geological formation. All coals are formed from vegetable growth 
fossilized by moisture, heat, pressure and time, and can be individually dis- 
tinguished by the physical structure as well as by the chemical peculiarities. 
A broad classification includes wood fiber or cellulose, which is the lowest of 
the group, followed in order by peat, lignite, bituminous coal, semi-bituminous. 



K) 



Oxygen- Percent 
15 20 25 30 



35 



40 



45 




95 90 85 80 75 70 65 60' 55 50 

Carbon - Percent 

Fig. 203. Grouping Coals according to Chemical Constituents. 



45 



semi-anthracite, anthracite coal and graphite. The differences in composition 
are shown in Fig. 203, based on data prepared by the Bureau of Mines. Start- 
ing from the lowest in the group, each succeeding variety of coal is distin- 
guished by an increase in carbon and a decrease in oxygen. The hydrogen 
remains practically constant for the lower part of the group but decreases 
rapidly in the higher part. The curve is plotted from analyses computed 
on a basis of coal free from moisture, ash, nitrogen and sulphur. Therefore, 
the sum of the carbon, hydrogen and oxygen content as given equals 100 
per cent. 

Wood is the representative of the organic substance from which coal is 
derived. The extreme variations of its properties explain the differences found 
in coal. The term wood includes trees, small plants, and mosses, which are com- 
posed chemically of cellulose, or of fiber and sap or sap deposits between the 
fibers. Actual wood has a higher carbon content than cellulose or moss. 
It contains from 15 to 25 per cent of moisture even when air dried. The 
ash content may be from 2 to 3 per cent. Dry wood has a heat value of 
8000 to 9000 B.t.u., and ordinary fire wood of 5000 to 6000 B.t.u. per pound. 

Peat is organic matter in the first stages of conversion to coal. It is 
found in swamps and bogs and consists of roots and fibers in every stage 
of decomposition, these containing 70 to 85 per cent of moisture. Its color 
varies from yellow, through brown, to black. Its percentage of nitrogen and 
oxygen is large and its volatile matter poorly combustible. Peat is valuable 



436 FUEL 



as a fuel only after having been thoroughly dried. Air-dried peat has a 
heat value of 9000 B.t.u., and when completely dry the value may be over 
10,000 B.t.u. per pound. 

Lignite, sometimes called brown coal, is the next step from peat 
in the formation of coal. It contains from 30 to 50 per cent of water, this 
being reduced by air-drying to from 10 to 20 per cent. Lignite is of a 
woody texture and does not coke on being carbonized. Its heat value 
is between 7000 and 8000 B.t.u. per pound, while the ash content varies 
from 5 to 10 per cent. As it disintegrates rapidly on exposure, lignite 
cannot be shipped any distance except in cold weather when frozen. 

Sub-bituminous coal is next to lignite in order of age. The chemical 
difference between it and lignite is not clearly defined and so it is sometimes 
called black lignite. However, the physical difference is marked. The sub- 
bituminous coal is black and shiny, has only a small trace of woody structure, 
contains less water and has a higher heat value than lignite. It differs from 
bituminous coals by the slacking it undergoes when exposed to the weather. 

Bituminous coal includes the so-called soft coals, which vary in color 
from dark brown to pitch black. The important divisions of this group are 
the caking and the non-caking coals ; both burn with a yellowish flame, and 
give off smoke. Caking coal has a tendency to fuse and swell in size during 
heating. lis high volatile content and richness in hydrocarbons make it valu- 
able in the manufacture of coal gas. Non-caking coal burns freely without 
fusing, is therefore well adapted to burning on grates without interfering 
with the air supply required for combustion, and is used extensively under 
steam boilers. The heat value is between 14,000 and 15,000 B.t.u. per pound. 

Semi-bituminous coal is brighter in appearance, and somewhat harder 
than bituminous coal, more nearly resembling anthracite. It is generally 
free burning, without smoke. It burns with a short flame and has a high 
heat value. 

Semi-anthracite coal is harder than semi-bituminous. It burns freely 
with a short flame, yielding great heat with little clinker and ash. It swells 
considerably in size but does not cake, and tends to split up on burning. 
Semi-anthracite when newly fractured will soil or soot the hand, while 
pure anthracite will not. There is only a small amount of this coal in the 
United States. 

Anthracite, commonly called hard coal, is practically all fixed carbon. It 
generally occurs with slate streaks, has a deep black color, and a shiny 
semi-metallic luster. It contains little hydrocarbon, is slow to ignite, and 
burns with a short yellowish flame which changes to a faint blue, but with 
little or no smoke. Anthracite does not sotten or swell, but breaks into 
small pieces when rapidly heated. Because the price of the coal decreases 
with the size, anthracite of less than V^-m. diameter is generally used for 
steam purposes. The smaller sizes often contain slate which cannot be dis- 
tinguished, so that the ash content is high. Anthracite has a specific gravity 
varying from 1.3 to 1.8. 

Graphite is the highest of the coal group but is not available for fuel 
because of the high temperature required for its ignition. While practically 
pure carbon it can be burned only with difficulty in the hottest fire and 
when mixed with other coals. 

The classification of coals by name, as above, is only a convenience. 
The different coals overlap to some extent and a technical description is 
necessary. For this purpose the chemical properties of the coals have 
generally been used, as shown in Table 64, by C. E. Lnckc. Campbell proposes 
a classification on the ratio of the total carbon (C) to the total hydrogen (H) 



FUEL 



437 



of the ultimate analysis. The coals are divided into twelve groups, but 
sufficient data to fix the values marked (?) are not available. Frazer sug- 
gests the fixed carbon (f. c.) divided by the volatile combustible matter 
(v. m.) of the proximate analysis, while Muck recommends the total carbon 
content of dry and ash free coal, as a standard. Another classification is 
based on the fixed carbon in the combustible, as in the last column of the 
tabulation. 



Table 64. Classification of Coal by Composition. 





Coal 

1 


Campbell 


Frazer 


Muck 


General 


Class. 


C 
H 


- f. c. 
v.m. 


%c 

in 
Combustible 


% f. c. 

in 

Combustible 


A 


Graphite and graphite 
coal 


00 to ? 


Anthracite 
100 
to 
12 


Anthracite 
95 




B 


Anthracite 


?to30 


Anthracite 






97 to 92.5 


c 


Anthracite 


30 to 26 








D 


Semi-anthracite 


26 to 23 


12 to 8 


92.5 to 87.5 


E 


Semi-bituminous 


23 to 20 


8 to 5 


Common 
Coal 

82 


87.5 to 75 


F 


Bituminous 


20 to 17 


Bituminous 
5 
to 



Bituminous, 






Eastern 
75 to 60 


G 


Bituminous.. . . 


17 to 14.4 








H 


Bituminous 


14.4 to 12.5 


Bituminous, 






Western 
65 to 50 


I 


Bituminous 


12.5 to 11.2 


J 


Lignite 


11.2 to 9.3 




70 


Under 50 








K 


Peat 


9.3 to? 


59 




L 


Wood or Cellulose. . . 


7.2 


50 





Cannel coal differs from the general group of coals and is therefore not 
included in the previous classification. It lies somewhere between bituminous 
and sub-bituminous but is considerably higher in hydrogen than either. It 
is said that the name is derived from the fact that this coal burns like a 
candle. Cannel coal is hard, dull black, easily broken, and gives a large 
amount of gas when heated. It is valuable, therefore, as an "enricher" in 
gas making. 



Location of Coal Deposits in the United States 

I 'HE map. Fig. 204, shows the areas in which coals are mined, the older de- 

^ posits being grouped into seven fields. Some graphite coal is found in 

Rhode Island ; most of the anthracite comes from Eastern Pennsylvania ; 

semi-bituminous comes mainly from the northeast section of the Appalachian 

field ; bituminous coals are found in the remaining larger fields ; sub-bitumi- 



FUEL 



439 




I Graph/ fe Vm-A Bifuminous 

\Anthracife lii!illllllill '5t/i? -bifuminous 
\Semi-bifummous ^^^^LJgnife 



1-R I- Graphite 5- Eastern Inferior 
2-Pa Anfhracife 6-Wesfern Inferior 
^-Appalachian 7-Soufhwesf Inferior 

■4-Norfhern Inferior 



Fig. 204. Coal Fields of the United States. 

nous is found mostly in the western states, and lignite comes from the 
South and Northwest. The coals from all these localities have been analyzed 
by the Bureau of Mines, the compositions being listed in Table 65. 

Composition of Coals 

T N burning coal, first the moisture is driven off. next the volatile matter, and 
■*■ then the remaining fixed carbon ignites, leaving a residue of ash. These 
four constituents of coal are ordinarily determined by the "proximate 
analysis," which gives information sufficient for all practical purposes. The 
chemical elements are accurately determined by the ''ultimate analysis" which 
gives the percentage of carbon, hydrogen, nitrogen, sulphur and ash. The per- 
centage of oxygen is taken as the difference between 100 and the sum of the 
other five constituents because there is no simple direct method of deter- 
mining it. 

The results for both analyses. Table 65, are for coal "as received," which 
means that the weight of moisture in the actual sample, as received at the 
laboratory or in the coal at the point of sampling in the mine, is included in 
the test samples. However, both proximate and ultimate analyses can be 
made or computed to a dry or "moisture free" condition or to a basis of 
"moisture-and-ash-free" coal. The moisture-free analysis gives the compo- 
sition and heat value of dry coal while the moisture-and-ash-free analysis 
gives the approxiniate composition and heat value of the dry combustible 
matter. Table 68, for a typical coal sample, indicates the three values. 



Commercial Sizes of Coals 

ThOR commercial purposes, coals are classified by trade names that desig- 
-*- nate the size, but the names and sizes vary in different localities. In 
bituminous fields this variation is marked, while in the anthracite trade a 
fair standard exists, as indicated in Table 66. 



440 



FUEL 



Table 65. Composition and Heat Value of United States Coals. 



County, Bed or Local Name 



Proximate Analysis 
"A5 Received" 



11 -bI 



Llriinate Analysis 
"As Received" 



>> 

O 



d o u 



Alabama 

Bibb, Belle Ellen 

Jefferson, Dolomite 

Jefferson, Littleton 

St. Clair,Da%-is Tillman Sta.) 

Shelby, Straven 

Tuscaloosa, Avernant 

Alaska 
Alaska Peninsula, Ciiignik 
Bay, Thompson Valley. . . . 

Bering River, Hartline 

Cook Inlet, Port Graham . . . . 
Matanuska.Matanuska River 
Seward Peninsula, Chicago 
Creek 

Arizona 
Navajo, Oraibi 

Arkansas 

Logan, Paris 

Pope, Russell%-ille 

Sebastian, Greenwood 

California 
Monterey, Stone Canyon. . . . 

Colorado 

Boulder, Lafayerte 

El Paso, Pikeview 

Garfield, Newcastle 

Montezuma, Cortez 

Weld, Platte%-ille 

Georgia 
Chattooga, Menlo 

Idaho 

Fremont, Hayden 

Illinois 

Clinton, *Germantown 

Franklin, Zeigler 

La SaUe, '=^La SaUe 

Macoupin, '^Staunton 

Madison, C ollins\-ille 

Marion, *CentraIia 

Montgomery, Panama 

St. Clair, *Shiloh 

Saline, Harrisburg 

Sangamon, =^Auburn 

Williamson, Carter^-ille 

Williamson, Herrin 

Indiana 

Clay, ^Brazil 

Greene, ^^Linton 

Knox, *Bicknell 



3.16 
3.16 
2.53 
3.39 
3.83 
2.62 



31.05 
25.40 
26.94 
30.69 
32.03 
24.18 



59.56 
67.75 
59.48 
57.08 
58.66 
64.11 



6.23 
3.69 
11.05 
8.84 
5.48 
9.09 



10.77 30.37 43.99 14.87 



4.75 

19.96 

1.72 



13.72 
3S.73 
24.36 



63.31 
32.46 
58.97 



18.22 

8.85 

14.95 



37j82 26.14 32.16 3.88 
9.88 32.64 46.86 10.62 



2.77 
2.07 
3.21 



14.69 

9.81 

14.84 



73.47 
78.82 
72.66 



9.07 
9.30 
9.29 



6.95 46.69 40.13 6.23 



19.15 

26.20 
4.45 
3.89 

28.90 



30.82 
29.67 
42.05 
37.01 
28.83 



44.27 
37.67 
49.56 
46.58 
37.25 



5.76 
6.46 
3.94 
12.52 
5.02 



3.80 15.88 65.83 14.49 
11.45 37.24 47.01 4.30 



11.35 
11.S2 
12.39 
13.54 
12.70 

9.95 
13.31 
11.69 

6.01 
16.00 

9.18 

8.80 



34.62 
27.66 
36.89 
35.69 
36.36 
34.76 
33.62 
35.70 
32.37 
32.41 
27.30 
29.85 



40.63 
55.10 
41.80 
40.03 
41.47 
42.06 
41.34 
39.42 
54.32 
37.82 
55.40 
53.83 



13.40 

5.42 

8.92 

10.74 

9.47 

13.23 

1L73 

13.19 

7.30 

13.77 

8.12 

7.52 



Parke, *Rosedale 

Pike, *Lirtles 

Sullivan, Dugger 

Vigo, *Macks%ille 

Warrick, Elberfeld 

Iowa 
Appanoose, *Centerville. 

Lucas, '^'Chariton 

Polk, =^Altoona 

Wapello, *Laddsdale. . . . 
Kansas 

Cherokee, *Scamnion 

Crawford, Fuller 

Leavenworth, Lansing. . . 
Linn, 'Jewett 



16.91 26.85 3S.S7 17-37! 
13.58 32.07 46.20 8.15 
12.08 32.48 44.42 11.02 



10.72 
11.12 
13.48 
12.82 
9.69 



39.29 
36.98 
32.51 
34.80 
38.59 



41.42 
42.55 
48.38 
42.08 
41.04 



8.5 < 

9.35 

5.63 

10.30 

10.68 



14.08 35.59 39.37 10.96 1 

15.39 30.49 41.49 12.63 

13.88 36.94 35.17 14.01 

8.24 30.74 45.02 16.00 

2.50 33.80 51J25 12.451 

4.85 33.53 52.52 9.10 

11.10 35.51 40.69 12.70 

9.04 29.69 45.55 15.72 



1.20 
0.56 
0.79 
2.34 
0.97 
0.64 



5.33 
5.05 
4.80 
5.18 
5.29 
4.72 



78.28 
S2.28 
74.44 
73. SI 
77.26 
77.52 



1.37 
1.36 
1.59 
1.53 
1.25 
1.48 



7.59 
7.06 
7.33; 
8.30; 
9.75 
6.55 



0.70 4.98 55.27 

0.62 3.14 65.93 

0.52 5.S1 49.53 

0.46 4.46 70.78 



0.65 6.12 41.79 0.67 45.89 
1.12 5.42 62.00 1.13 19.71 



2.79 4.02 78.71 
1.74 3.62 80.28 
3.12 3.75 78.37 



1.46 
1.47 
1.52 



3.95 
3.59 
3.95 



4.17 6.28 66.01 1.17 16.14 



0.25 
0.30 
0.44 
7.04 
0.46 



5.93 
6.13 
5.43 
4.96 
6.64 



56.38 
49.36 
72.57 
66.19 
48.36 



1.08 
0.66 
L72 
1.16 
0.93 



30.60 
37.09 
15.90 
8.13 
38.59 



1.27 4.32 70.59 1.09 8.24 
0.54 5.94 68.09 1.40 19.73 



4.76 
0.46 
3.92 
4.03 
3.67 
3.87 
3.75 
4.38 
1.66 
4.05 
0.90 
1.13 



5.41 
5.44 
5.S5 
5.71 
5.81 
5.25 
5.19 
5.46 
5.27 
5.55 
5.10 
5.08 



57.36 
67.87 
61.29 
58.69 
60.91 
59.64 
59.07 
57.15 
71.63 
53.89 
68.45 
68.70 



1.05 

1.34 
1.00 
0.95 
0.99 
1.04 
0.95 
0.94 
1.34 
0.91 
1.14 
1.33 



18.02 
19.47 
19.02 
19.88 
19.15 
16.97 
19.31 
18.88 
12.80 
21.83 
16.29 
16.24 



14,141 
14,616 
13,286 
13,363 
13,799 
13,729 



0.61 23.57 i 9,641 

1.32 10.77 10,820 

0.92 34.37 8,793 

1.42 7.93 12,585 



1.89 5.48 52,97 1.01 21.28 
0.91 5.65 63.53 1.42 20.34 
3.65 5.34 60.45 0.89 18.651 



3.83 
3.78 
L09 
3.27 
4.79 



5.86 
5.63 
5.94 
5.66 
5.39 



63.48 
63.01 
66.01 
61.16 
62.36 



1.16 
1.13 
1.49 
1.03 
1.28 



4.26 5.57 58.49 0.90 

3.19 5.74 55.81 1.14 

6.15 5.52 54.68 0.84 

5.03 4.81 59.82 0.94 



17.10 
17.10 
19.84 
18.58 
15.50 

19.82 
21.49 

18.80 
13.40 



10,800 

13,774 
13,702 
13,588 

12,477 

9,616 

8,352 

13,129 

12,341 

8,465 

12,791 

12,094 

10,733 

11,961 
11,399 
10,807 
10,989 
10,960 
10,548 
10,999 
12,793 
9,940 
12,015 
12,222 

9,524 
11,419 
11,011 

11,767 
11,549 
11,788 
11,119 
11,412 

10,723 
10,242 
10,244 
11,027 



5.68 


4.91 


69.07 


1.20 


6.69 


12,900 


4.95 


5.08 


71.20 


1.24 


8.43 


12,942 


3.99 


5.30 


60.72 


1.13 


16.16 


11,065 


3.72 


5.01 


60.99 


1.06 


13.50 


11,142 



"^Indicates samples from car deliveries; all others are mine samples. 



FUEL 



441 



Table 65. Composition and Heat Value of United States Coals — Cont. 



County, Bed or Local Name 



Proximate Analysis 
"As Received" 









Ultimate Analysis 
"As Received" 



3 
Of 

m 






c 
o 

C4 

u 



X 

O 



0)1-] > 
CS « S 

t> ft <u 

*J 3^ 
a A m 



K 



Kentucky 

Johnson, Flambeau 

Muhlenberg, Central City 

Ohio, McHenry 

Pike, Hellier 

Webster, "Wheatcroft 

Maryland 

Allegany, Eckhart 

Allegany, Frost burg 

Allegany, Lord 

Allegany, Midland 

Allegany, Washington 

Michigan 

Saginaw, Saginaw 

Missouri 

Adair, Kirksville 

Caldwell, Hamilton 

Henry, Windsor 

Lafayette, Napol^n 

Macon, Bevier 

Ray, Richmond 

Montana 

Carbon, Bear Creek 

Cascade, Geyser 

Custer, Miles 

Fergus, Lewistown 

Missoula, Missoula 

Yellowstone, Musselshell . . 
New Mexico 

Colfax, Raton 

Lincoln, White Oaks 

M'Kinley, Blackrock 

North Dakota 

Morton, Leith 

M'Lean, *Wilton 

Stark, *Lehigh 

Williams, *Williston 

Ohio 

Belmont, *Bellaire 

Guernsey, *Danford 

Jackson, *Wellston 

Jefferson, Amsterdam 

Noble, Belle Valley 

Perry, *Dixie 

Oklahoma 

Coal, Lehigh 

Haskell, McCurtajn 

Pittsburg, Carbon 

Pittsburg, McAlester 

Oregon 

Coos, Beaver Hill 

Pennsylvania 

Allegheny, Bruceton 

Allegheny, Oak Station 

Allegheny, Scott Haven . . . , 

Bedford, Hopewell 

Cambria, Barnesboro 

Cambria, Beaverdale 

Cambria, CarroUtown Road 

Cambria, Fallen Timber 

Cambria, Hastings 

Cambria, Johnstown 



2.36 
8.73 
9.89 
3.73 
6.29 



2.70 
3.20 
2.26 
3.10 
3.40 



48.40 
37.76 
35.94 
30.01 
31.97 



14.50 
14.50 
16.05 
15.50 
15.00 



38.75 
45.93 
43.36 
59.42 
54.13 



74.00 
75.60 
75.86 
74.50 
75.10 



10.49 
7.58 

10.81 
6.84 
7.61 

8.80 
6.70 
5.83 
6.90 
6.50 



11.91 31.50 49.75 6.84 



15.98 
10.99 
13.51 
13.44 
16.25 
13.56 

9.67 
8.76 
29.13 
15.35 
24.70 
16.66 



38.15 
35.00 
33.24 
32.00 
33.38 
34.29 

35.92 
25.72 
25.33 

28.27 
29.33 

27.85 



37.18 
41.37 
41.88 
40.27 
40.97 
40.66 

46.39 
50.36 
30.51 
48.08 
26.11 
48.07 



8.69 
12.64 
11.37 
14.29 

9.40 
11.40 

8.02 
15.16 
15.03 

8.30 
19.86 

7.42 



2.12 36.06 50.22 11.60 

2.52 34.63 45.99 16.86 

14.69 34.93 41.56 8.82 



36.18 29.77 

35.96 31.92 

35.38 29.59 

36.78 28.16 



4.14 
6.65 
7.71 
3.50 
5.15 
7.55 



39.30 
33.94 
38.32 
37.98 
37.34 
38.00 



7.07 36.41 

2.70 21.07 

2.09 27.59 

3.58 32.11 



25.35 
24.37 
25.68 
29.97 

47.18 
48.86 
42.02 
51.08 
49.00 
46.08 

45.68 
69.88 
50.25 
59.04 



8.70 
7.75 
9.35 
5.09 

9.38 
10.55 
11.95 

7.44 
8.51 
8.37 

10.84 
6.35 

20.07 
5.27 



16.10 31.10 39.63 13.17 



2.73 
3.48 
2.60 
1.58 
2.87 

3.44 
0.93 
3.34 
2.89 
1.32 



36.03 
35.15 
32.67 
16.32 
21.44 

16.18 
23.10 
24.06 
23.67 
14.63 



54.98 
55.45 
59.41 
69.98 
69.23 

73.46 
69.29 
62.75 
66.34 
75.24 



6.26 
5.92 
5.32 
12.12 
6.46 

6.92 
6.68 
9.85 
7.10 
8.81 



1.20 
2.65 
3.64 
0.56 
1.35 



1.00 
0.92 
0.79 
0.86 
1.04 



6.47 
5.52 
5.37 
5.07 
5.49 

4.44 
4.51 
4.68 
4.57 
4.63 



71.98 
67.65 
62.27 
76.30 
69.78 



79.21 
80.99 
82.45 
80.71 
80.69 



1.16 
1.42 
1.33 
1.06 
1.37 



1.69 
1.77 
1.73 
1.69 
1.55 



8.70 
15.18 
16.58 
10.17 
14.40 

4.86 
5.11 
4.52 
5.32 
5.60 



1.24 5.84 66.56 1.19 18.33 



4.12 
4.81 
4.08 
3.08 
3.41 
3.77 

1.64 
3.91 
0.55 
4.53 
0.85 
1.00 



5.90 
5.43 
5.89 
5.62 
5.75 
5.65 

5.52 
4.40 
5.60 
5.42 
5.56 
5.61 



59.09 
60.40 
59.16 
55.83 
58.25 
58.1,6 

6.166 
58.93 
40.09 
61.15 
39.04 
59.22 



0.94 
1.16 
0.85 
0.98 
1.05 
1.04 

1.48 
0.79 
0.54 
0.71 
0.74 
0.97 



21.26 
15.56 
18.65 
20.20 
22.14 
19.89 

21.68 
16.81 
38.19 
19.89 
33.95 
25.78 



0.64 4.94 69.96 1.33 11.53 
0.76 4.97 66.65 1.32 9.44 
0.79 5.82 60.93 1.12 22.52 



0.68 6.76 39.45 0.59 

1.15 6.54 41.43 1.21 

1.55 6.61 40.23 0.54 

0.48 6.93 41.87 0.69 



3.64 
0.77 
5.73 
0.56 



5.19 
5.30 
5.41 
5.43 
5.42 
5.48 

5.13 
4.46 
4.46 
5.31 



69.58 
67.38 
62.49 
73.39 
70.51 
67.02 

64.38 
81.33 
63.66 
77.11 



1.20 
1.20 
1.11 
1.46 
1.50 
1.29 

1.44 
1.67 
1.33 
1.62 



43.82 
41.92 
41.72 
44.94 

10.69 
12.44 
14.43 
9.19 
11.12 
15.00 

14.57 
5.42 
4.75 

10.13 



0.81 5.53 51.07 1.19 28.23 



1.39 
1.18 
0.77 
1.94 
1.52 

1.83 
1.30 
1.80 
1.37 
1.57 



5.26 
5.42 
5.39 
4.09 
5.00 

4.64 
4.81 
4.96 
5.02 
4.26 



76.82 
75.73 
78.16 
77.01 
80.53 

80.61 
81.64 
76.78 
79.49 
81.19 



1.46 
1.45 
1.45 
1.44 
1.19 

1.20 
1.26 
1.25 
1.30 
1.39 



8.81 
10.30 
8.91 
3.40 
5.30 

4.80 
4.31 
5.36 
5.72 
2.78 



13,770 

12,208 
11,392 
13,649 
12,874 



13,910 
14,100 
14,483 
14,070 
14,160 



11,781 

10,798 
11,093 
10,779 
10,232 
10,625 
10,771 

10,832 
10,127 

6,662 
10,615 

6,727 
10,226 

12,965 
11,956 
10,809 

6,700 
7,069 
6,923 
7,204 

12,874 
12,179 
11,515 
13,286 
12,733 
12,128 

11,468 
14,098 
11,695 
13,615 

9,031 

13,815 
13,700 
14,085 
13,408 
14,177 

14,114 
14,485 
13,618 
14,107 
14,047 



*Indicates samples from car deliveries; all others are mine samples. 



442 



FUEL 



Table 65. Composition and Heat Value of United States Coals — Cont. 



Coxmt\-, Bed or Local Name 



Proximate Analysis 
"As Received" 



3 :5 i 



>2 fc,^ 



Ultimate Analysis 
"As Received" 



3 






^ c 



3 J -J 



Pennsyl vania — C ontinue d 

Cambria, Nanty Glo 

Cambria, Portage 

Cambria, St. Benedict 

Cambria, Van Ormer 

Cambria, Vintondale 



Cambria, Windber 

Center, Osceola Mills 

Clarion, Blue Ball Station 

Clearfield, Boardman 

Clearfield, Philipsburg 



Clearfield, Smoke Run. . 
Fayette, Connellsville. . . 

Indiana, Cl>Tner 

Indiana, Glen Campbell. 
Jefferson, Sykesville 



Lackawanna, Diinmore. 

Luzerne, Pittston 

SchuvDdll, Miners\alle. . 
Schuylkill, Tower City. 
Somerset, Jerome 



Somerset, MacDonaldton. . . 

Somerset, "Windber 

Sullivan, Lopez 

Washington, Marianna 

Westmoreland, Greensburg. 

Rhode Island 

Newport, Portsmouth 

Providence, Cranston 

South Dakota 

Perkins, Lodgepole 

Tennessee 

Anderson, Brice\ille 

Campbell, LafoUette 

Rhea, Da>-ton 

Texas 

Houston, Crockett 

Wood, Hoj-t 

Utah 

Carbon, Sunnyside 

Emery, Emery 

Iron, Cedar City 

Summit, Coahille 

Virginia 

Henrico, Ga\ton 

Lee, Darb>'\-ille 

Russell, Dante 

Tazewell, Pocahontas 

Wise, Georgel 

Washington 

King, Black Diamond 

King, Cumberland 

Elittitas, Roslyn 

Pierce, Carbonado 

Thurston, Centralia 

West Virginia 

Fayette, Carlisle 

Fayette, Fayette 

Fayette, Hawks Nest 

Fayette, Kay Moor 

Fayette, MacDonald 



2.84 
3.52 
2.94 
2.73 
3.63 

3.30 
2.08 
1.90 
2.95 
0.90 

3.73 
3.24 
2.06 
3.08 
2.44 

3.43 
2.19 
2.76 
3.33 
1.44 

1.03 
2.40 
3.16 

1.44 
2.14 

22.92 
4.54 



19.78 
17.32 
19.52 
24.98 
18.63 

12.50 
21.46 
22.00 
21.29 
21.59 

20.29 
27.13 
24.46 
27.32 
28.44 

6.79 
5.67 
2.48 
3.27 
15.21 

16.03 
13.50 
8.59 
34.61 
30.02 

2.78 
3.01 



70.89 
73.27 
70.87 
63.64 
71.20 

77.90 
69.87 
66.30 
66.92 

68.49 

68.41 
62.52 
66.09 
61.16 
60.68 

78.25 
86.24 
82.07 
84.28 
73.38 

72.57 
77.80 
78.08 
57.77 
58.81 

58.37 
78.69 



6.49 
5.89 
6.67 
8.65 
6.54 

6.33 
6.59 
9.80 
8.84 
9.02 



1-0 I 

7.11 
7.39 
8.44 
8.44 

11.53 
5.90 

12.69 
9.12 
9.97 

10.37 
6.31 

10.17 
6.18 
9.03 

15.93 
13.76 



1.85 
1.06 
1.76 
0.81 
1.98 

1.04 
1.99 
1.95 
1.35 
1.99 

1.33 
0.95 
2.19 
1.29 
1.32 

0.46 
0.57 
0.54 
0.60 
0.90 

2.22 

1.26 
0.67 
0.78 
1.17 



4.87 
4.78 
5.04 
4.89 
4.90 

4.46 
4.92 
4.66 
4.74 
4.57 

4.86 
5.24 
5.08 
4.99 
5.07 

2.52 
2.70 
2.23 
3.08 
4.17 

4.29 
4.44 
3.47 
5.23 
5.03 



80.83 
82.06 
79.78 
78.24 
80.59 

81.65 
80.58 
78.05 
78.51 
79.49 

78.92 
78.00 
79.39 
76.71 
76.91 

78.85 
86.37 
79.22 
81.35 
79.43 

79.17 
82.62 
79.49 
78.76 
76.33 



1.32 
1.23 
1.26 
1.22 
1.23 

1.27 
1.29 
1.14 
1.19 
1.31 

1.22 
1.23 
1.19 
1.27 
1.31 

0.77 
0.91 
0.68 
0.79 
1.34 

1.24 
1.31 
1.10 
1.44 
1.56 



4.64 
4.98 
5.49 
6.19 

4.76 

5.25 
4.63 
4.40 
5.37 
3.62 

6.10 

7.47 
4.76 
7.30 
6.95 

5.87 
3.55 
4.64 
5.06 
4.19 

2.71 
4.06 
5.10 
7.61 
6.88 



14,285 
14,278 
14,143 
13,860 
14,119 

14,340 
14,274 
13,760 
13,901 
14,060 

13,970 
13,919 
14,170 
13,772 
13,732 

12,782 
13,828 
12,577 
13,351 
13,799 

13,700 
14,370 
13,376 
14,242 
13,662 



0.10 2.84 58.46 0.18 22.49 8,528 
0.87 0.46 82.39 0.12 1.75i 11,624 



39.16 24.68 27.81 8.35 2.22 6.60 38.02 0.53 44.2? 



1.70 35.02 53.14 10.14 
2.92 32.04 58.23 6.81 
1.76 27.86 49.57 20.81 



34.70 32.23 21.87 

33.71 29.25 29.76 

5.96 38.68 48.77 

3.93 40.92 49.22 

10.35 36.33 43.70 

14.20 36.00 44.80 



2.81 
3.42 
2.76 
3.50 
2.48 

7.98 
5.84 
3.89 
3.81 
25.08 

4.95 
3.22 
5.00 
3.17 
3.22 



25.70 
34.36 
34.96 
15.50 
31.71 

37.69 
31.32 
37.00 
26.60 
32.25 

lg.l6 
22.28 
24.50 
25.11 
17.53 



62.47 
58.83 
56.51 
76.80 
60.30 

45.95 
36.46 
46.49 
49.33 
34.02 

73.75 
71.68 
67.20 
68.81 
76.46 



11.201 

7.28 I 

6.59 
5.93, 
9.62 
5.00 

9.02 
3.39 
5.77 
4.20 
5.51 

8.38 
26.38 
12.62 
20.26 

8.65 

3.14 
2.82 
3.30 
2.91 
2.79 



1.06 4.97 75.32 1.80 6.71 

1.14 5.19 74.95 1.62 10.29 

0.49 4.51 66.24 1.19 6.76 

0.79 6.93 39.25 0.72 41.11 

0.53 6.79 42.52 0.79 42.09 



1.73 5.43 71.28 

0.39 5.52 73.02 

5.82 5.13 61.24 

1.41 5.79 61.40 



6,307 

13,462 
13,514 
11,666 

7,056 
7,348 



1.52 13.45 12,841 

1.25 13.891 12,965 

0.95 17.241 10,874 

1.09 25.311 10,630 



1.43 
0.58 
0.59 
0.73 
0.52 

0.45 
0.47 
0.37 
0.39 
0.82 

0.82 
0.55 
0.55 
0.52 
0.64 



4.90 
5.25 
5.32 
4.77 
5.59 

5.60 
4.80 
5.58 
5.01 
6.37 

5.09 
5.11 
5.12 
5.09 
5.01 



76.55 
77.98 
80.13 
83.36 
79.69 

64.79 
52.77 
68.55 
63.85 
47.26 

82.15 
83.07 
80.06 
82.59 
84.11 



1.81 
1.29 
1.43 
1.08 
1.56 

1.69 
1.30 
1.31 
1.93 
.91 

1.48 
1.56 
1.38 
1.63 
1.56 



6.29 
11.51 
6.76 
5.86 
7.13 

19.09 
14.28 
11.57 
8.56 
35.99 

7.32 
6.89 
9.59 
7.26 
5.89 



13,493 
14,134 
14,148 
14,630 
14,252 

11,732 

9,529 

12,434 

11,518 

8,170 

14,434 
14,702 
14,280 
14,584 
14,760 



*Indicates samples from car deliveries; all others are mine samples. 



FUEL 



443 



Table 65. Composition and Heat Value of United States Coals — Cont. 





Proximate Analysis 
"As Received" 


Ultimate Analysis 
"As Received" 


,4k 


County, Bed or Local Name 


Moisture 

Volatile 
Matter 

Fixed 
Carbon 

Ash 


Sulphur 
Hydrogen 

Carbon 

Nitrogen 

Oxygen 


Heat Value 
B.t.u. per L 
"As Receiv 


West Virginia — Continued 

Fayette, Page 


3.32 28.88 62.72 5.08 

2.94 19.69 68.67 8.70 
1.66 32.89 59.94 5.51 
2.80 14.50 77.40 5.33 
2.30 16.98 76.21 4.51 

2.19 13.91 75.25 8.65 
3.32 16.22 76.35 4.11 
3.25 14.46 78.05 4.24 
2.55 13.44 78.57 5.44 
2.32 16.76 69.80 11.12 

3.00 13.00 78.80 5.23 

2.95 35.01 56.44 5.60 
3.43 14.58 77.89 4.10 
3.58 13.17 79.10 4.15 
1.63 28.42 62.01 7.94 

1.40 26.40 62.92 9.28 
3.30 14.00 77.60 5.14 
3.02 16.06 78.75 2.17 
1.12 20.74 70.38 7.76 

17.29 31.33 45.89 5.49 
11.45 42.58 39.33 6.64 
21.27 32.83 42.75 3.15 
15.86 33.01 47.39 3.74 
16.02 33.63 47.60 2.75 
23.88 34.33 38.44 3.35 


0.80 5.29 79.73 1.37 7.73 
1.86 4.70 77.66 1.45 5.63 
0.93 5.16 78.97 1.26 8.17 
0.64 4.56 83.39 1.03 5.05 
0.66 4.36 85.00 1.20 4.27 

0.57 4.45 80.69 1.19 4.45 
0.55 4.67 83.05 1.16 6.46 
0.48 4.65 84.05 1.12 5.46 
0.57 4.58 83.60 1.01 4,80 
1.78 4.35 77.46 1.27 4.02 

0.48 4.46 82.84 1.05 5.94 
0.67 5.33 77.89 1.38 9.13 
0.67 4.79 83.79 1.06 5.59 
0.56 4.90 83.59 1.07 5.73 
0.96 5.00 78.24 1.28 6.58 

1.50 4.83 77.92 1.43 5.04 
0.63 4.60 82.94 1.41 5.28 
0.80 5.02 85.02 1.40 5.59 
1.05 4.52 81.22 1.59 3.86 

0.35 5.64 59.15 0.85 28.52 
0.38 5.27 59.66 0.94 27.11 
0.89 6.13 55.91 0.75 33.17 
0.59 6.06 62.03 1.29 26.29 
0.94 6.11 62.29 1.08 26.83 
0.38 6.29 54.07 1.14 34.77 


14,209 


Fayette, Sun 


13,786 


Logan, Holden 


14,126 


M'Dowell, Ashland 


14,550 


M'Dowell, Big Four 


14,636 

13,995 

14,587 


M'Dowell, Coalwood 

M'Dowell, Eckman 


M'Dowell, Ennis 


14,571 
14,569 
13,514 

14,500 
13,862 
14,602 
14,598 
13,937 

13,808 
14,490 


M'Dowell, Powhatan 

M'Dowell, Roderfield 

M'Dowell, Worth 


Marion, Monongah 


Mercer, Coaldale 

Mercer, Wenonah 


Monongalia, Richard 

Preston, Masontown 

Raleigh, Sophia 


Raleigh, Stonewall 


15,001 


Tucker, Thomas 

Wyoming 

Bighorn, Cody 

Carbon, Hanna 


13,800 

10,055 
10,890 


Fremont, Hudson 


9,779 


Hot Springs, Kirby 

Sweetwater, Superior 

Sheridan, Monarch 


10,984 

10,849 

9,335 



♦Indicates samples from car deliveries; all others are mine samples. 





Prepared with square- 
mesh screens 


Prepared with round- 
mesh screens 


Sizes 


Through 

mesh 
opening, 

inches 


Over 

mesh 

opening, 

inches 


Through 

mesh 

diameter, 

inches 


Over 

mesh 

diameter, 

inches 



Broken (furnace) 

Egg 

Stove 



4 
2 



2M 
2 



2^ 






Nut (chestnut) 


'A 


Va 
Va 


1K2 

Vie 1 


y% 


Pea 

Buckwheat No. 1 


Vie 

Vie 


Buckwheat No. 2 (rice) 

Buckwheat No. 3 (barley) 


M 


y% 


Vie 1 
Vie 1 


Vie 
Vie 











In some instances a No. 4 Buckwheat has been marketed ; and some mines 
supply "Birdseye" which is practically a mixture of Nos. 2 and 3 Buck- 
wheats, or "through Vie and over Vie." 




Hotel Claridge, New York City, equipped with Heine BoUers. 



FUEL 445 



For the sizing of bituminous coals the American Society of Mechanical 
Engineers has recommended the following: 

EASTERN BITUMINOUS 
Lump coal must pass over a 1^-in. mesh bar screen. 
Nut coal must pass through a V/i-'m. mesh, and over a %-in. 
screen. 

Slack coal must pass through a ^-in. bar screen. 

WESTERN BITUMINOUS 
Lump coal comes in 6-in., 3-in. and V/s.-m. sizes, and the respective 
lumps must pass over circular openings of corresponding size. Where 
the lump coal is sized as 6 by 3 in. and 3 by 1^ in., the coal must 
pass through the larger opening and over the smaller. 

Steam nut of 3-in. size must pass through a 3-in. circular opening 
and over a \%-m. mesh. Nut of 1^-in. size must pass through a 
1^-in. and over a ^-in. opening, and %-in. coal must pass through a 
^-in, mesh and over a 5^-in. opening. 

Coal screenings must pass through a 1^-in. round mesh. 
In the coal fields "run-of-mine" is the name given to the unscreened 
coal taken from the mine, and "culm" is the residue from screenings, in- 
cluding "silt" and other anthracite dust. 

Sampling Coal 

SAMPLES taken at the mine, says G. S. Pope, are generally of higher 
grade than those obtained from the average commercial shipments. The 
former contain a lower percentage of ash and have a higher heat value. 
Persons without experience generally select a sample better than the average 
run of the coal delivered. However, an experienced collector, by using good 
judgment, can obtain samples so fairly representative that the results of 
the analyses are reasonably accurate.. 

The value of laboratory analysis has been questioned largely because of 
ignorance or carelessness in taking the samples. The laboratory test makes 
use of one gram — about V28 of an ounce — of coal. The particles of coal in 
this sample should have been a considerable and equal distance apart in 
the original bulk shipment. A representative sample can be obtained only 
by repeated and systematic crushing, dividing and discarding — such as is 
described below. 

The sample should contain about the same proportions of fine and 
coarse coal as well as foreign matter, such as slate and bone, in order to 
show the quality of the coal delivered as a whole. To this end portions of 
coal are selected from all parts of the wagon, car, or ship, then mixed and 
systematically reduced to the quantity required for analysis. The original 
or gross sample should weigh 500 lb. or more, preferably 1000 to 2000 
pounds. The Bureau of Mines has established a 1000-lb. sample as sufficient 
to give reliable results for coal comparatively free from impurities. For 
other coals a larger sample is required. Increasing the size of the gross 
sample tends toward accuracy, but the possible increase is limited by the 
cost of collection and reduction. A separate sample should be taken from 
each 500 tons or less of coal delivered. The gross sample is usually reduced 
to quantities varying between 2 to 5 lb. and then sent to the laboratory. 

Representative sam.ples can best be taken during the time when the coal 
is being loaded or unloaded. Portions of 10 to 30 lb., depending upon the 
size and weight of the largest pieces of coal, should be systematically taken 
with a shovel or a specially designed tool. The mechanical method is pre- 
ferred to shovel sampling, as it eliminates the personal equation. Care 
should be exercised to secure equal amounts of coal from near the top, the 
middle and bottom of the load. Clean boxes, buckets or ash cans may 



446 



FUEL 



be used for holding the portions of coal that make up the gross sample. The 
receptacles should have tight-fitting lids which can be locked, to prevent 
gain or loss in moisture and to preserve the integrity of the sample. 

The next step is to prepare the 1000 lb. gross sample for shipment to 
the laboratory. Three operations are involved : crushing, mixing and reduc- 
tion in quantity. These can be done by mechanical means, using a so-called 
sample grinder, or else by the hand method described by the Bureau of Mines, 
which involves six stages, Fig. 205, to obtain the final 5 lb. sample. 

In this procedure the coal must be broken down to the sizes given in 
Table 67, before division into equal parts. The lumps can be crushed with 
a tamper, maul or sledge, on a hard, clean, dry floor free from cracks. Other 
tools required are a shovel, broom and rake ; also a blanket measuring about 
6 by 8 ft. The coal is raked while being crushed, so that all lumps will be 
broken. The floor or blanket is swept clean of discarded coal after each 
sample has been divided into equal parts. The space where this is done 
should be protected from rain, snow, wind and direct sunlight. 

The alternate-shovel method of reducing the gross sample, as shown in 
the first and second stages in Fig. 205, is repeated until the sample is reduced 



Table 67. Largest Sizes of Coal Allowable in Samples. 



Stage of 
Preparation 


Weight of 
Sample, Lb. 


Size of 
Coal, inches 


1 

2 
3 


1,000 
500 
250 


1 


4 
5 
6 


125 
60 
30 


16 



to about 250 pounds. Before each reduction in quantity the sample should 
be crushed to the fineness prescribed in Table 67. 

The crushed coal is shoveled into a conical pile as in diagrams 2 and 7, 
by depositing each shovelful of coal on top of the preceding one, and then 
formed into a long pile as follows ; 

The sampler takes a shovelful of coal from the conical pile and spreads 
it out in a straight line as in diagrams 3 at A and 8 at A, the width being 
that of the shovel and the length, from 5 to 10 feet. His next shovelful is 
spread directly over the top of the first shovelful, but in the opposite direc- 
tion, and so on back and forth, the pile being occasionally flattened until 
all the coal has been formed into one long pile, as shown in diagrams 3 and 
8 at B. 

The sampler then discards half of his pile, and beginning at one side 
of the pile, at either end, and shoveling from the bottom of the pile, takes 
one shovelful (No. 1, in diagrams 4 and 9) and sets it aside; advanc- 
ing along the side of the pile a distance equal to the width of the shovel, he 
takes a second shovelful (No. 2) and discards it; again advancing in the same 
direction one shovel v.idth. he takes a third shovelful (No. 3), and adds 
it to the first. Shovelful No. 4 is taken in a like manner and discarded, 
the fifth shovelful (No. 5) is retained, and so on, the sampler advanc- 
ing always in the same direction around the pile, so that its size will be 
reduced uniformly. When the pile is removed, about half the original 



FUEL 



447 



coal should be contained in the new pile formed by the alternate shovelfuls 
which have been retained. The retained halves are shown at A and the 
rejected halves are shown at B, in diagrams 5 and 10, Fig. 205. 

After the gross sample has been decreased by the above method to 
about 250 lb., the quantity is further reduced by the quartering method. 
Before each quartering, the sample should be crushed to the fineness de- 
scribed in Table 67. 

Quantities of 125 to 250 lb. should be thoroughly mixed by coning and 
reconing, as in diagrams 12 and 13 ; quantities less than 125 lb. should be 
placed on a cloth or blanket, measuring about 6 by 8 ft. ; mixed by 
raising first one end of the cloth and then the other, as in diagrams 18, 24 
and 30, so as to roll the coal back and forth ; and after being thoroughly 
mixed, formed into a conical pile by gathering the four corners of the 
cloth, as in diagrams 19, 25 and 31. 

The conical pile is quartered by flattening the cone, its apex being pressed 
vertically down with a shovel or board. The flattened mass, which must be 
of uniform thickness and diameter, is then marked into quarters, as in 
diagrams 14, 20, 26 and 32, by two lines that intersect at right angles directly 
under a point corresponding to the apex of the original cone. The diagonally 




*<ilBiH||||||infll< 




Fig. 206. Bureau of Mines Coal Sample Containers. 

opposite quarters, B in diagrams 16, 22, 28 and 34, are shoveled away and 
discarded and the space that they occupied brushed clean. The coal remain- 
ing is successively crushed, mixed, coned and quartered until two opposite 
quarters equal approximately 10 lb. of Vie-inch size. This 10-lb. quantity is 
divided into two equal parts. Each part is immediately sealed into a container 
for transportation. One of the samples is forwarded for analysis to the 
laboratory and the other held in reserve, should the sample forwarded be 
lost or damaged in transit. 

One or more containers can be used for this purpose, depending upon 
the quantity they will hold. Glass jars or metal cans of one or two-quart 
size are ordinarily employed. 

The Bureau of Mines has developed two sample holders. Fig. 206, one 
a galvanized iron can and the other a double container consisting of a wooden 
shipping box and an inclosed pressed-paper case. The metal can is 11 in. 
long and 3^ in. diameter, inside dimensions, with a screw cap 2 in. diameter. 
The capacity is 2^2 to 3 lb. of coal, so that two cans are used for the 
laboratory sample. Before filling, each can should be carefully inspected as to 
tightness and freedom from rust. The coal should then be carefully packed 
in, so as to occupy as much of the space as possible and exclude the air. 
This can be accomplished by shaking or jarring the container repeatedly and 
vigorously while filling it. The screw cap is then closed against a rubber 
washer. To insure tightness, the cap when screwed down in place is wrapped 
carefully with electrician's rubber or adhesive tape, the first layer of which 
completely covers the joint, as at a in Fig. 206. At b the can is shown 
properly sealed and ready to be wrapped for mailing. Solder, paraffin or 
sealing wax should not be used, because some of it may become mixed 
with the coal, either when it is applied or when the cap is removed. 



448 



FUEL 




Crush 1,000-pound sample on 
hard, clean surface to 1" size 



1,000-pound sample crushed 
to 1" and coned 



2nd STAGE 



Mix by forming long pile. 
i4— spreading out first shovelful. 
P— long pile completed 




Crush 500-pound sample 
(# 5,i4)to5i" sir© 



500 pounds crushed 1o^" and ooned Mix by forming long pile. " 



A— spreading out first shovelful. 
£— long pile completed 




Crush 250-pound sample 250-pounds crushed to 1^" and cofied |^ix by forming new cone 

(# 10. A)io Vz" size 




Crush 125-pound sample {^ \^: A, A) 
on blanket to?^" size 



Mix by rolling on blanket 



Form cone after mixing 



5th STAGE 




— ~£:~ . — — = 


— 


J?^^^'«-^-5^ 


"^^y^-. 


-:rT=_- -=^ 


=^===^.=i^^-^ 23 



Crush 60-pound sample (y^ 22; A, A) Mix bv rolling on blanket 

to 54" size 




Form cone after mixing 




Crush 30-peund sample {:f^2Q: A, A) |Vlix by rolling on blanket 

to'^^e" or 4-rr;sh size 



Form cone after mixing 



Fig. 205. Preparation of Coal Sample by Hand. 

(Read straight across both pages.) 



FUEL 



449 




Halving by alternate shovel nriethod. 

Shovelful* 1, 3, 5, etc., reserved a« 5, A; 

2, 4, 6. etc., rejected as 5, B 



Long pile divided into two parts; 
A — reserve; 5— reject 




Halving by alternate ttiovel method. 

Shovelfuls 1, 3, 5, etc., reserved ulQ,A', 

2. 4. 6, etc., rejected aslO, B 




Long pile divided into two parts; 
A — reserve; P— reject 




Quarter after flattening cone 



Sannple divided into quarters 



Retain opposite quarters A, A. 
' Reject quarters B, B 




o 




— ~'^' - — /'~A' ~ 




'^ 


^W^^5- - 


7 

22 




2*^---i' ~-4 - — -X 


— _. — 




'— ■ ^=^ 


— 



Quarter after flattening cone 



Sanriple divided into quarters 



Retain opposite quarters A, A. 
Reject quarters B, B 




Quarter after flattening cons 



Sample divided into quarters 











f 

28 







: "" --^s=^ — — — 



Retain opposite quarters A, A. 
Reject quarters B, B, 




Quarter after flattening con» 



Sample divided into qtiarters 



Fill two 5-pound, sample containers from 
JL, At one for laboratory, one for reserve 



Fig. 205. Preparation of Coal Sample by Hand. 

( Read straight across both pages. ) 



450 



FUEL 



In the double container shown at the right. Fig. 206, c is the pressed 
paper case, d and e sections of the wooden box, and f the assembled con- 
tainer. The paper case. 5>s in. diameter and 7 in. long, has a capacity of 
5 to 7 lb. of coal. The shipping box is made of well-seasoned basswood 
with lock-jointed comers, fulh- reinforced. Two suit-case catches are placed 
near opposite comers, inside the box, to operate in either of the two possible 
ways of assembh'. Small holes are drilled through opposite sides of the 
box, as at g. and through a small part of the catch lug. By releasing the 
catches with a nail inserted in the two holes, the box is easily opened. In 
using this container, the sample of coal is placed in the paper case and the 
edge of the cap is sealed tight with adhesive tape. 

With each container sent to the laboratory- for analysis, there should be 
a ticket bearing the name and address of the plant, the date, the kind and 
size of coal, the number of tons represented by the sample, and other similar 
information. This form, properly tilled in, can be placed inside the container 
or preferably around the container on the outside, before wrapping for 
mailing. A copy should be retained for reference or checking. 

Fuel Analysis 

HP HE term moisture, as used in fuel analyses, represents the loss in weight 
-■- of a coal sample when dried for a given time at a given temperature. This 
is taken as the total moisture in the coal received at the laboratory*. 

Volatile matter is the gaseous combustible matter of the coal and 
represents the hydrocarbons and other gaseous compounds which distill off 
on application of heat, as well as some incombustible gases. 

Fixed carbon is the solid combustible matter represented by the uncom- 
bined carbon in the coal or the carbon remaining after distillation. It is 
not pure carbon nor is it the total carbon in the coal, for a part of the 
carbon is expelled as volatile matter. 

Ash is the incombustible remaining after the moisture and volatile matter 
have been driven from the coal and the fixed carbon burned; it is the 
residue left from complete combustion of the coal. 

These four items are set forth in the proximate analysis, which may 
show them in either of three different ways. The whole four items may 
be given in one statement, as in the second column of Table 68. known as 
'"as received." The moisture may be stated separate!}- or ignored, and the 
other three items given as in the third column ; and this is known as 
■'moisture free" or '"dr}- coal."" The ash also may be stated separately, and 
the other two items given as in the fourth column, known as ■"combustible" 
or "moisture and ash free.'"' 

Table 68. Proximate Coal Analvsis Statements. 



Constituent 


As received, 
Per cent 


Moisture-free, 
Per cent 


Moisture and 
ash-free, 
Per cent 


Moisture 

Volatile matter 

Fixed Carbon 


10 
30 
50 


'33.'33 'ST.'SO 
ho .56 62 . 50 


Ash 


10 
100 


11.11 




Total 




100.00 


100.00 



The foUov.-ing instructions for the proximate and ultimate analyses of 
coal, and for the analyses of liquid fuels are taken from the 1915 Code of 
the American Societ}- of Mechanical Engineers. 



FUEL 451 

Proximate Analysis of Coal. The apparatus required for proximate 
analysis consists of a mill for grinding coal, chemical scales sensitive to 
Viooo of the amount weighed, drj'ing apparatus, a platinum crucible, a Bun- 
sen burner and blast lamp, a supply of oxygen gas, and such chemicals and 
chemical apparatus as may be required. The elements to be determined are 
moisture, volatile matter, fixed carbon, ash and sulphur. 

Determine the loss from air-drying and the total moisture in the ash 
as received, as explained elsewhere. 

To determine volatile matter, place about one gram of the air-dried 
powdered coal in the crucible and heat in a drying oven to 220° F. for 
one hour (or longer if necessary to obtain minimum weight), cool in a desic- 
cator and weigh. Cover the crucible with a loose platinum plate. Heat 7 
minutes with a Bunsen burner giving a 6 to 8 in. flame, the crucible being 
supported 3 in. above the top of the burner tube and protected from outside 
air currents by a cylindrical asbestos chimney 3 in. diameter. Cool in a 
desiccator, remove the cover, and weigh. The loss in weight represents the 
volatile matter. 

In the U. S. Bureau of Mines practice a 1-gram sample of fine (60- 
mesh) air-dried coal is heated to a temperature of 1750° F. in a plat- 
inum crucible with a close-fitting cover for seven minutes over a No. 3 
Meker burner giving a flame 16 to 18 cm. high. The crucible is placed 
so that its bottom is 2 cm. above the top of the burner. To protect 
the crucible from the efi^ects of drafts it is surrounded by a sheet iron 
chimney of special design. The loss in weight minus the weight of 
moisture determined at 220° F. represents the volatile matter. 
To ascertain the ash, expose the residue in the crucible to the blast 
lamp until it is completely burned, using a stream of oxygen if desired to 
hasten the process. The residue left is the ash. 

The Bureau of Mines determines the ash in the residue from the mois- 
ture determination. The moisture is determined by heating 1 gram 
of the 60-mesh air-dried coal in a porcelain crucible for one hour at 
220° F. in a constant temperature heating-oven. To determine the 
ash, the crucible is heated slowly in a muffle furnace until the volatile 
matter is driven off. Ignition in the muffle is continued at a tempera- 
ture of 1380° F., with occasional stirring of the ash until all the par- 
ticles of carbon have disappeared. The crucible is cooled in a desic- 
cator, weighed, heated again for half an hour, and weighed again. 
The process is repeated until the variation in weight between two 
successive ignitions is 0.0005 gram or less. 
The difference between the residue left after the expulsion of the volatile 
matter and the ash is the fixed carbon. 

To determine sulphur by Eschka's method, which is the one com- 
monly used, a sample of 60-mesh coal weighing 1.3736 grams is mixed in a 
30 cc. platinum crucible with about 2 grams of Eschka mixture (2 parts 
light calcined magnesium oxide, 1 part anhydrous sodium carbonate) and 
about 1 gram of the Eschka mixture is spread over it as a cover. The mixture 
is carefully burned out over a gradually increasing alcohol or natural gas 
flame. When all black particles are burned out the crucible is cooled, the con- 
tents digested with hot water, filtered, washed, and the solution treated with 
saturated bromine water and hydrochloric acid, boiled, and the sulphur pre- 
cipitated as barium sulphate by adding a solution of barium chloride. 

Ultimate Analysis of Coal. The apparatus required for ultimate analj^sis 
consists of a mill and other apparatus for grinding and pulverizing the coal ; 
chemical scales sensitive to Viooo of the amount weighed; drying apparatus; 
combustion apparatus, embracing a combustion furnace, a glass combustion 
tube one end of which is filled with copper oxide and chromate of lead and 
the other end with a roll of oxidized copper gauze, a porcelain boat, a set of 




o 
CD 

V 

G 
'v 



a 
a 

"5 
v 



O 



CO 

(Z4 



CO 

x: 
O 

d 
U 

CQ 

PQ 

V) 

B 

CO 

< 

V 
Xi 

H 



V U ]'. T. 453 



l)ull)S containing hydrate of potassium, a U-tul)e filled with chloride of 
calcium, and a sui)ply of pure oxygen and pure air; together with .suita1)lc 
chemicals and chemical apparatus required for the various processes. The 
elements to l)e determined are moisture, carhon, hydrogen, oxygen, sulphur, 
nitrogen, and ash. 

The moisture is determined in the manner as pointed out above. 

The carhon and hydrogen are obtained by the use of the combustion 
apparatus. One-half gram of the pulverized oven-dried coal is placed in the 
porcelain boat, which is introduced between the copper roll and the copper 
oxide within the combustion tulje. After the contents within have been thor- 
oughly dried out by a sufficient preliminary heating aided Ijy a current of 
dry air, the furnace is set to work and the coal burned by first passing air 
through the tube and finally oxygen, conducting the products of comlmstion 
through the potash bulbs and the chloride of calcium tube. The carbon 
dioxide produced by the combustion of the carl)on is absorbed by the ])()tash, 
and the water formed by the coml)Ustion of hydrogen is taken up by the 
chloride of calcium. The quantity of carbon is determined by weighing the 
bulbs before and after, thereby obtaining the weight of the carbon dioxide 
produced, and then calculating the weight of carbon from the known compo- 
sition of the dioxide. Likewise, the quantity of hydrogen is determined by 
weighing the calcium tube l)efore and after, which gives the amount of water 
produced, and, dividing by 9, the amount of hydrogen. 

Sulphur is found by the method described above under the heading 
Proximate Analysis. 

To determine nitrogen, a certain weight of coal is mixed with strong 
sulphuric acid and permanganate of potash and heated until nearly colorless. 
This process converts the nitrogen into ammonia and then into sul])hate of 
ammonia, and the amount of sulphate is determined l)y making the solution 
alkaline and then distilling it. The nitrogen is found by calculation from the 
known composition of ammonia. 

The ash is found by weighing the refuse left in the combustion boat 
after the coal is completely burned. 

The oxygen is the difference between the sum of the elements previously 
determined and the original weight of coal. 

The ultimate analysis of coal, as will be seen from the above descrip- 
tion, requires the use of so much chemical apparatus, and at best it is so com- 
plicated that it is not likely to be done except in a fully equipped chemical 
la])oratory. It should not be undertaken by one who is not entirely familiar 
with all the details of the work. 

Analysis of Liquid Fuels. The determination of carbon and hydrogen 
in liquid fuels is made in the same manner as that concerning the solid fuels 
above descril)ed, using special means for preventing loss in the various 
processes on account of the volatile characteristics of the fuel. 

To determine the sulphur, the oil or other liquid is heated with nitric 
acid and barium chloride. The quantity of sulphate of Ijarium thus ])ro(luced 
is ascertained by filtering and weighing, and the sulphur calculated from the 
known composition of the compound. 

The ultimate analysis of liquid fuel, like that of coal, should be under- 
taken only by a person familiar with all the necessary details. 

Heat Value of Coal 

The heal value of coal is represented by the heat unit.<; liberated by 
-*• perfect combustion and is usually expressed in British thermal units 
per pound of fuel. This value can be approximated from either tiie proxi- 
mate or ultimate analysis. 

From its proximate analysis the B.t.u. value of one pound of coal is 
given by Lucke as : 



454 



FUEL 



B.tu. = 14,544 c + 27,000 



"\ 4 + 0-5 ) 



(57) 



in which c and v are the fractional weights of fixed carbon and volatile, 
respectively, in the coal. 

From its ultimate analysis the B.tu. value of coal can be approximated 
by the Dulong formula 



B.t.u. = 14.544 C + 62,028 (h— -^\ -f 4050 6" 



(58) 



in which C is carbon, H is hydrogen. O is oxygen and S is sulphur, expressed 
as the fractional part of one pound of coal. 



K>.000 



!IS^ 



'BlOOC 



l<BOO 



.40 



Volatile in Combustible -% 
2D 




Fixed Carbon in Combustible- °ia 

Fig. 207. Heat Value of Coal by Proximate Analysis. 

Based on the proximate analysis of samples of coals, ]Vm. Kent has estab- 
lished a relation between the heat value and the fixed ^arbon as well as the 
volatile matter in the combustible, as shown in Fig. 207. The figures give a 
useful approximation and are correct within the indicated limits. 




500 1000 1500 :::: zsoo " 3000 " 5^0 " 4000 

Hydrogen. Btt.u. 
Fig. 208. Heat Value of Coal by Ultimate Analysis. 



FUEL 



455 



A graphical method of determining the heat value of coal, developed by 
W. C. Stripe, is shown in Fig. 208. The diagram is based on the ultimate 
analysis and corresponds with the formula by Dulong, given above. Knowing 
the constituents of the coal from the ultimate analysis, connect the values on 
the left-hand scale with the diagonals as shown by the dotted lines, and read 
the results on the lower scales. The sum of the three determined values will 
give the total approximate heat value of the coal. 

Fig. 208 is for a coal containing 79.9 per cent carbon ; 4.98 per cent 
hydrogen; 4.31 per cent oxygen; 1.85 per cent nitrogen; 1.13 per cent 
sulphur ; 7.83 per cent ash and 2.91 per cent moisture. The dotted-arrow 
lines show that the carbon represents 11,660 B.t.u. ; the hydrogen, for the 
oxygen content given, represents 2,750 B.t.u. ; and the sulphur represents 
45 B.t.u. Adding these values gives 14,455 B.t.u. as the approximate heat 
value of the coal. 

A more direct and accurate method of determining the heat value of 
coal is by a fuel calorimeter of the "bomb" type. A sample of the coal is 
burned in the bomb or combustion chamber, which is immersed in water. The 
heat of combustion, transmitted to the water, raises its temperature and from 
this rise the heat value of the coal is calculated. 



Mahler Coal Calorimeter 

I 'HE Mahler coal calorimeter consists essentially of a strong cylindrical 
-■■ vessel having a capacity of about 800 cc, which is closed at the top 
and filled with oxygen gas, under a pressure of 300 lb. per sq. in. A sample 
of finely powdered coal which will pass through a 100-mesh sieve, weighing 
about 1 gram, is placed in a pan suspended within the interior vessel pro- 
vided with two electrodes through which an electric current from a battery 
can be passed. The whole is immersed in an outer vessel containing about 




Fig. 209. Mahler Bomb Calorimeter. 

2500 grams of water, thoroughly stirred, the temperature of the water ob- 
served, the coal set on fire by completing the electric circuit, the water 
again stirred, and the temperature observed at intervals of half a minute 



FUEL 



457 



until the thermometer ceases to rise. The difference between the initial 
and final temperatures thus determined is corrected for radiation, the latter 
being found by observing the rate at which the temperature changes before 
and after the coal is fired. 

The weight of water contained in the outer vessel is added to the water 
equivalent of the apparatus, and the sum of the two is multiplied by the cor- 
rected rise of temperature expressed in deg. cent. The heat generated in 
burning the fuse wire, the heat due to the formation of aqueous nitric acid, 
and that due to the combustion of sulphur to sulphuric acid, are subtracted 
fiom this product. The remainder, divided by the weight of fuel expressed 
in grams, is the heat of combustion expressed in gram-calories per gram. 
This result is multiplied by 1.8 to convert to heat of combustion expressed 
in B.t.u. per lb. 

The correction for iron fuse wire is 1.6 calories per milligram. The 
correction for nitric acid, which is obtained by titrating the washings 
with standard ammonia solution (0.00587 grams of NH3 per cc.) is 5 
gram-calories per cc. of the ammonia solution. The correction for sul- 
phur, which is obtained by precipitation as barium sulphate is 13 gram- 
calories per 0.01 gram of sulphur. 

The sample used for the calorimeter test should be powdered and 
air-dried at the temperature of the room. A duplicate sample should be taken 
for the determination of the moisture in this air-dried coal by heating in a 
drying oven to 220° F. for one hour (or longer if necessary to obtain mini- 
mum weight), cooling in a desiccator and weighing. The results obtained 
on the calorimeter test should be corrected for the moisture thus found 
and reported as being referred to dry coal. 

Ash 

A SH is a mechanical mixture of silicates, oxides and sulphates. The 
^*' composition of ash in different coals is given in Table 69, due to 
/. S. Cosgrove. The amount of ash in coals varies with the locality of the 
mine, and for coal from the same district, with mining conditions. Depend- 
ing on the kind and size of coal, the ash content is from 3 to 25 per cent. 
The nominal amount of ash is that contained in the face sample of coal 
taken from the seam proper ; this amount is usually increased by ash added 
from the roof or bottom in the course; of mining. 

Table 69. Composition of Constituents in Percentage of Total Ash. 



Constituent 



Anthracite 



Semi- 
Bituminous 



Bituminous 



(a) 



(b) 



Bitumiinous 
Slack 



Lignite 



Sulphur Oxide (SO2) . . 

Silica (SiOa) ... 

Calcium Oxide (Lime) 

(CaO) 

Alumina (AI2O3) 

Iron Oxide (Fe203). . . . 
Magnesium Oxide 

(MgO)..... 

Potassium Oxide 

(K2O) 

Sodium Oxide (Na20) 
Total Ash, per cent . . 



0.17 
25.66 

1.56 
27.03 
42.83 

11.83 



7.26 



1.00 
54.80 

1.40 

29.20 

6.80 

0.60 

2.10 
1.90 
7.50 



0.10 
47.30 

1.20 

34.60 

9.80 

0.40 

2.50 

2.10 

17.40 



26.90 
15.20 

18.10 

8.60 

13.30 

10.00 

1.80 
5.30 
8.20 



0.40 
53 . 20 

1.00 
26.00 
15.80 

0.70 

1.60 

0.30 

11.40 



12.50 
39.30 

14.90 

24.08 

3.80 

1.70 

0.40 

0.10 

16.60 



458 



FUEL 



Run of mine and prepared sizes of coal made over a U^^-in. screen can 
be improved b}- removing the excess ash by hand. Impurities amounting 
to 12 per cent have been taken out in this manner. It is advisable, therefore, 
to wash, screen or hand-pick the impurities before shipping' the coal! 
Accordmg to L. J. Jotfray, the washing of coal at the mine will reduce 
the excess ash in screenings, so that the heat value approaches that of 
lump bituminous, as shown by these figures : 

Ash per cent. B.tu. per lb. 

Dry or unwashed screenings 22.61 8.895 

Washed screenings 14.05 10aS5 

Lump 12.39 10^499 

These are actual values and refer to coal taken from one mine in the 
Central West. 

The relation bet^^-een ash content and heat zahic can be established for 
anj- particular coal. Fig. 210 has been determined by M. B. Smith on a 
basis of 1800 samples of Hocking Valley slack coal.' The samples came 
from 20 different mines and were tested over a long period. It is stated that 
the figures in the diagram agree, within 10 to 50 B.t.u., with actual calo- 
rimeter tests. The average proximate analysis of this coal is: 

Fixed carbon, per cent 52.60 

Volatile, per cent 34.20 

Ash, per cent _ 13 20 

Sulphur, per cent- 1 80 

Heat value, B.t.u. per lb 12.300 

Moisture as received, per cent 9.85 



\AfiOO 



13^000 



^12,000 



3 

V 



11,000 



IQOOO 



1 


■ 1 






j 1 




1 






, 1 


\ ! 




I 


> 

X 




X 


: 1 ^\ ! 


i ' \ : 


X 






' 1 \ 




1 


1 N^ ' I 1 




\ 


\ 


\ 


1 ' 1 


^i 1 


III i 1 


>»J 


\ 


1 i \ 


1 


N 


1 

, i , 1 





5 10 15 20 25 

/fsA //r Dry Coa/^ Per cert 

Fig. 210. Relation between Heat and Ash Content. 



FUEL 



459 



The evaporation is related to ash content as shown in Fig. 211, due to 
W. N. Polakov. With an increase of ash the evaporation falls, rapidly at 
first and more slowly when the percentage is high. Large excess of air 
and additional losses due to frequent cleaning accompany the use of coal 
of high ash content. 



9.0 



m 

o 
o 



I- 



8.6 



8.4 



8.? 



8.0 



2 7. 



o 

Q. 
<0 

1^ 



7.6 



« 74 






7.2 



ZO 



■ O ■ 


3 






























\ 


^ n 
































\ 
































\ 
































o 


^ 
































\ 
































\ 


o 






























s 


I 




o 


o 


























\ 
































A 






















1 
1 








' 1 


V 




















1 

i 










\ < 


5 






























n 


\ 
































\ 






























\ 


\ 


o 






o 
























\ 








3 


























^ 






O 



























<^r 


\ 








i 


^ 
























\ 


S^ 
































V. 




^ 









1^ 16 IS 20 22 24 26 28 

Ash in Dry Coal, per cent. 

Fig. 211. Relation between Evaporation and 
Ash Content of Coal. 



30 



Clinker 

CLINKER is formed bv the mechanical adhesion of the particles of ash, 
or by the fusion of the ash to form slag. Some of the constituents of 
ash act as alloys and form a fused mass of clinker known as "'running 
ashes." Clinker can be classified as "hard" and "soft" by these character- 
istics : 

Hard clinker is the result of the direct melting of the ash or some of 
its components. When due to the fusing of the ash, the clinker will form 
a large, hard cake. When due to the melting of some of the ash constit- 
uents the clinker will be distributed throughout the ash in the form of small 




c8 




a 








S 




u 




V 




H 






1 


4J 




V 


l-H 


V 


^ 


u 


o 




00 
C3 




u 


>> 




t> 


2 


^ 


u 







^ 


d 


V 


U 


(-■ 




•4-1 


T) 




OS 


c 


o 


• ^* 


u 






c 


"3 


.2 


(^ 


"•2 




CO 


o 






"ffl 


2 




O 


_c 


c3 


u 


o 


u 


o 


"5 


a 


n 


'-Ij 






u 


Qt 


c 


PQ 






V 


V 


ffi 




CU 





K 




o 




o 




o 





FUEL 



461 



hard chunks. Hard clinker hardens while in the ash on the grates. It is 
usually the direct result of bad firing methods. 

Soft clinker is not directly chargeable to poor firing, but poor firing 
may start the formation and hasten the spread of clinker. Soft clinker is 
caused by the slagging of the ash, that is, the silica of the ash combines 
with the base having the lowest fusing temperature. After having formed, 
the clinker continues to grow until the whole grate is covered. In appearance 
it is not unlike hard clinker, having a crust on top although fluid beneath 
the surface. Soft clinker varies in consistency from a thick paste to a 
heavy oil ; the more fluid it is, the faster it spreads, remaining molten while 
on the grate but hardening when the temperature is lowered. 

Fusion of Ash. For the constituents of ash, the fusing temperatures (in 
degrees Fahrenheit) are as follows : 

Sulphur (S) 239 Alumina (AI2O3) 3416 

Silica (SiOa) 3227 Calcium oxide (CaO) 3452 

Iron (Fe) 2840 Magnesium oxide (MgO)....3882 

All the fusing temperatures (except sulphur) are higher than those found 
in a boiler furnace. 

The efifect of clinker is shown in Fig. 212, due to /. P. Sparrow. The 
tests were made on boilers equipped with standard stokers. The efficiency 
remained constant up to 2335 degrees. Above this the efficiency increased 
rapidly with a small rise in temperature, but beyond 2475 deg., the efficiency 
remained constant up to 2900 degrees. The critical point of ash-fusion is 
between 2400 and 2500 degrees. If the ash-fusion temperatures are below 
2400 deg., the coals are classed as clinkering, and if above 2500 deg., as 
non-clinkering. The standard ash-fusion temperature is taken as 2450 deg., 
with a variation of 50 deg. plus or minus. 



80 



79 



78 



a: 77 

T3 

c. 
E 76 

o 
O 



75, 




































































































f 


























i 


/ 
































/ 


























J 




























7 




















































































2200 2500 



2400 2500 2600 2700 2800 

Ash Fusion Tempera+ure, de3. Fahr. 
Fig. 212. Effect of Clinker on Efficiency. 



2900 



The clinkering behavior of coal is indicated in Table 70, due to L. J. 
J off ray, which gives results from burning tests. The coals with non-clinkering 
ash listed in the table were low in sulphur and in lime, and did not clinker 
at 2900 deg. in a dazzling white fire. The ash in the clinkering coals fused 
at a temperature of 2200 deg., because the sulphur and lime content were 



462 FUEL 

high in proportion to the silica, alumina, and the iron oxide. Sulphur 
content alone does not indicate that the coal may clinker, although with 
normal ash content and 4 per cent or more sulphur, the coals listed have 
such a tendency. 

Table 70. Ash Behavior of Coal from Illinois and Indiana Mines. 



Test 

No. 



Ash in r. 1 1. Heat Value, 

Drj- Coal, Sulphur, g t_u, CUnker Color of Ash 

per cent. P^'' cent. pgj. u^ 



1 


9.63 


0.64 


12.325 


Xo 


White 


2 


10.30 


1.30 


12.1.36 


Xo 


White 


3 


10.00 


1.19 


12.368 


Xo 


Light Gray 


4 


12.73 


2.96 


12.389 


Yes 


Reddish Grav 


5 


11.80 


4.43 


11.768 


Slightlv 


Reddish Gray 


6 


13.85 


4.02 


ll.&i2 


Yes 


Reddish Gray 


7 


12.80 


4.52 


11.693 


Yes 


Reddish Grav 


8 


17.96 


4.58 


11.124 


Yes 


Reddish Gray 


9 


8.48 


1.47 


12,251 


Xo 


White 


10 


12.49 


4.50 


11,921 


Yes 


Dark Gray 



Investigations of the Bureau- of Mines on the fusibility of ash have 
been compiled in Table 71. The softening temperatures represent the 
average point of fusion. In making the tests, the ash samples were molded 
into solid triangular pj-ramids -^-d-in. high and ^:;-in. along the base. These 
were mounted in a vertical position and fused down to a spherical lump. 
The values thus obtained in the laboratory are said to be comparable with 
those obtained in the actual boiler furnace. 

The softening temperatures in Table 71 vary from 1900 to 3100 degrees. 
Above 2400 deg., little trouble should be experienced from clinkering. The 
temiperatures have been grouped into three classes, as follows: (1) Refrac- 
tor\- ashes softening above 2600 deg. (2) Ashes of medium fusibility, soft- 
ening between 2200 and 2600 deg. (3) Easily fusible ash, softening below 
2200 deg. The coals of high softening temperatures are from the lower or 
older beds. The bituminous fields of Penns3'lvania, however, give a more 
refractory ash than similar beds in West Virginia. The ash from the anthra- 
cite districts is very refractory and the softening temperatures are usually 
above 3000 degrees. 

The softening or fusing temperature of ash is a measure of its clink- 
ering qualities, although seldom included in coal specifications. This is 
undoubtedly due to the many difficulties surrounding the temperature deter- 
mination, and to the fact that no definition of melting temperature has been 
accepted as standard. 

Clinkering in boiler furnaces is due to thick or heavy fires, excessive 
stirring of fuel beds, live coals in ashpit, too much slack in the coal, 
closed ashpit doors, or to the admission of pre-heated air under grates. 

With thick fires the air supply is decreased, so that the ash becomes 
heated. In an atmosphere furnishing oxj-gen, the melting point of ash is 
higher than if it is heated in a reducing atmosphere. A considerable thick- 
ness of ash is mixed with the burning coal in the thick fuel bed, and on 
account of the lower air velocitj-. a reducing zone exists near the grate. 
In the thin fire the reducing zone is confined to the last inch or two, at the 
top, where the few ash particles are separated and cannot fuse into clinker. 



FUEL 



463 



Table 71. Fusibility of Ash from the Coals of the United States. 

ALABAMA 



Location and Bed 



Black Creek. 

Clark.. 

Coal City. . . 
Gholson. . . . 
Harkness. . . 

Helena 

Jagger 

Jefferson . . . . 
Mary Lee. . . 





Percent in 


Soften- 
ing 


Dry Coal 






Temp. 


of 


of 


Deg. 


Ash 


Sulphur 


2,530 


3.31 


0.83 


2,350 


8.68 


1.06 


2,250 


4.35 


1.10 


2,240 


6.64 


0.73 


2,460 


11.51 


1.57 


2,430 


8.91 


0.46 


2,690 


9.81 


0.67 


2,120 


7.45 


2.80 


2,830 


9.90 


0.74 



Location and Bed 



Soften- 
ing 
Temp. 
Deg. 



Percent in 
Dry Coal 



of 
Ash 



of 
Sulphur 



Maylene 

Montevallo. . . 
Nickel Plate. . . 

Pratt 

Thompson. . . . 
Upper Straven 
Yellow Creek. . 
Youngblood . . . 



2,350 
3,330 
2,620 
2,430 
2,230 
2,340 
2,370 
3,130 



8.29 
7.24 
4.73 
5.49 
8.85 
7.45 
13 . 90 
8.62 



0.45 
0.76 
0.75 
1.59 
0.52 
0.88 
2.91 
1.08 



ARKANSAS 



Denning. . . 
Hartshorne. 



2,200 
2,120 



7.38 
11.59 



2.45 
1.40 



Paris 

Sluin Basin 



2,140 
2,180 



3.38 
2.23 



10.12 
10.36 



ILLINOIS 



No. 


1 Bed 


2,110 


11 


74 


4 


86 


No. 


6 Bed 


2,160 


10 


27 


2 


30 


No. 


2 Bed 


2,010 


9 


97 


3 


58 


No. 


7 Bed 


2,050 


10 


62 


2 


69 


No. 


5 Bed 


1,990 


10 


84 


3 


28 

















INDIANA 



No. 3 Bed 
No. 4 Bed 
No. 5 Bed 



2,090 


10.61 


4.34 


2,390 


8.17 


1.62 


2,130 


10.23 


3.54 



No. 6 Bed, 
Minshall. . 



2,040 
2,120 



9.91 
9.80 



KANSAS 



2.65 
2.99 



Bevier . . . 
Cherokee . 



1,980 
2,110 



14.83 
9.42 



Leavenworth . . . . 
Weir-Pittsburgh. 



2,020 
2,010 



18.26 
11.68 



5.46 
5.31 



KENTUCKY 



No. 6 Bed 
No. 9 Bed 
No. 10 Bed 
No. 11 Bed 
No. 12 Bed 

Alum 

Elkhorn. . . 
Fire Clay . . 

Flag 

Harlan. . . . 
Hazard .... 
Hickory. . . 



2,130 


8.81 


2.97 


2,030 


10.53 


3.67 


1,990 


11.99 


4.18 


2,030 


9.57 


4.08 


2,150 


10.20 


2.30 


2,940 


4.37 


0.61 


2,470 


3.83 


0.68 


2,790 


5.35 


0.82 


2,880 


7.52 


0.83 


2,700 


3.94 


0.85 


2,460 


8.56 


0.79 


2,340 


5.37 


1.07 



Jellico 

Kellioka 

Lower Boiling. . . 
Lower H ignite. . . 
LowerStandiford 

Mason 

Miller Creek. . . . 
Poplar Lick , . . . 

Rawl 

Straight Creek . . 

Thacker 

Upper Hance. . . 



2,460 


6.92 


2,830 


2.21 


2,880 


11.65 


2,440 


4.57 


2,260 


5.24 


2,320 


3.93 


2,160 


4.33 


2,670 


5.30 


2,680 


7.53 


2,110 


3.40 


2,430 4.42| 


2,330 


4.74 



1.56 
0.49 
1.01 
1.10 
1.81 
1.14 
1.90 
1.05 
1.90 
1.17 
1.39 
1.61 



464 



FUEL 



Table 71. Fusibility of Ash from the Coals of the United States — Cont. 

MARYLAND 



Location and Bed 



Soften- 
ing 
Temp. 
Deg. 



Percent in 
Dry Coal 



of 

Ash 



of 

Sulphur 



Location and Bed 



Soften- 
ing 
Temp. 
Deg. 



Percent in 
Dry Coal 



of 

Ash 



of 
Sulphur 



Bakerstown 

Bluebaugh 

Brush Creek. . . . 

Clarion 

Franklin 

Gallitzen 

Grantsville 

Little Pittsburgh 
Lower Freeport. . 



3,560 


10.26 


1.70 


2,770 


12.99 


1.63 


2,470 


9.61 


1.26 


2,280 


9.61 


2.42 


2,410 


8.48 


1.36 


2,140 


12.15 


3.33 


2,490 


8.23 


1.22 


3,010 


7.95 


1.18 


2,150 


20.51 


4.11 



Lower Kittaning. 

Mercer 

Pittsburgh 

Quakertown 

Split-Six 

Lpper Freeport. . 
L'pper Kittaning. 
L'pper Sewickley. 
Waynesburg . . . . 



2,440 


10.76 


2.620 


18.14 


2,930 


7.67 


3,010 


17.03 


2,220 


12.42 


2,500 


10.72 


3,010 


9.50 


2,840 


6.65 


2.410 


13.75 



2.26 
3.28 
1.03 
2.92 
2.55 
2.03 
0.86 
1.09 
2.58 



MLSSOURI 



Bevier 

Bowen 

Cainsville 

Cherokee 

Jordan 

Lexington 

Lower Richhill 



1,960 


13.47 


4.90 


1,940 


13.18 


4.61 


1.980 


12.71 


5.78 


2,150 


7.51 


1.97 


2,010 


12.74 


4.42 


2,000 


13.48 


4.04 


1,940 


15.39 


5.43 



Lower- Weir- 
Pittsburgh 
Mulberry. . . . 

Milk\' 

Richhill 

Tebo 

Waverly 



1,940 


10.78 


1,990 


14.58 


1,940 


11.28 


1,970 


15.47 


2.040 


11. &1 


2,020 


17.43 



4.45 
3.18 
5.25 
6.12 
4.66 
8.29 



omo 



Anderson 


2,120 


10.86 


3.92 


Pittsburgh 


2,210 


8.47 


3.58 


Lower Freeport. . 


2,280 


9.55 


2.95 


L'niontown 


2,230 


16.10 


3.58 


Lower Kittaning. 


2,120 


9.24 


5.72 


Upper Freeport.. 


2,280 


8.48 


3.09 


Mahoning 


2,OiO 


6.59 


3.67 


Washington 


2,520 


21.90 


2.98 


Meigs Creek. . . . 


2,330 


13.02 


4.23 


Waynesburg 


2,400 


15.92 


3.15 


Middle Kittaning 


2,450 


8.00 


1.86 











OKLAHOMA 



Dawson. . . . 
Henryetta. . 
Lehigh Coal. 
Lower Hart- 
shorne .... 
McAllister . . 



1,920 
1,980 
2,150 

2,020 
2,180 



8.95 

8.03 

11.46 

6.03 
6.94 



3.91 
1.59 
4.17 

1.43 
1.67 



McCurtain. 
Panama. . . . 

Stigler 

L^pper Hart- 
shorne. . . 



2,110 
2,160 
2,050 


6.92 
6.81 
5.13 


2,170 


6.15 



0.84 
1.46 
1.91 

1.51 



PENNSYLVANIA i^Bituminous Region^ 



Bloss 

Brook\'ille 

Fulton 

Little Pittsburgh 
Lower Freeport. . 



2,630 


11.96 


2.25 


2,809 


12.98 


1.86 


2,940 


7.36 


1.18 


2,390 


8.13 


1.70 


2,390 


8.52 


2.06: 



Lower Kittaning. 
Middle Kittaning 

Pittsburgh 

Upper Freeport. . 
Upper Kittaning. 



2,550 


7.86 


2,380 


11.06 


2,360 


7.17 


2,350 


9.35 


2,350 


8.67 



2.03 
2.98 
1.43 
2.13 
2.16 



FUEL 



465 



Table 71. Fusibility of Ash from the Coals of the United States — Cont. 
PENNSYLVANIA — Continued — (Districts in Anthracite Region) 





Soften- 
ing 

Temp. 
Deg. 


Percent in 
Dry Coal 


Location and Bed 


Soften- 
ing 

Temp. 
Deg. 


Percent in 
Dry Coal 


Location and Bed 


of 
Ash 


of 
Sulphur 


of 
Ash 


of 
Sulphur 


East Schuylkill . . 

Hazelton 

Pittston 

Plymouth 


2,990 
2,960 
3,010 
3,010 


11.19 

14.50 

6.03 

12.52 


0.78 
0.61 
0.58 
0.84 


Scranton 

Shamokin 

West Schuylkill.. 
Wilkesbarre 


3,010 
2,960 
2,730 
3,010 


12.39 

16.59 
18.07 
13.17 


0.79 
0.90 
0.82 
0.78 



TENNESSEE 



No. 4 Bed ... . 
No. 10 Bed. .. 

Angel 

Battle Creek. . 

Billygpat 

Blue Gem. ... 
Bon Air No. 2 
Castle Rock. . 

Catoosa 

Coal Creek. . . . 
Frozen Head . . 
Grassy Ridge . 

Hooper 

Jellico 

Jordan 

Kelly 

Lower Dean . . . 
Mingo 



2,220 


9.08 


3.62 


2,150 


11.42 


3.14 


2,160 


5.80 


1.94 


2,520 


9.68 


1.52 


2,600 


3.26 


1.12 


2,100 


3.32 


1.34 


2,180 


10.27 


3.24 


2,260 


10.78 


2.68 


2,250 


7.11 


2.59 


2,260 


6.30 


2.37 


2,680 


6.92 


0.92 


2,470 


3.75 


1.87 


2,330 


2.58 


0.69 


2,350 


4.95 


1.87 


2,320 


3.33 


0.90 


2,530 


7.63 


1.33 


2,340 


3.69 


0.72 


2,390 


4.25 


1.27 

1 



Monarch 

Morgan Spring. 

Mud Slip 

Nelson 

Old Eagle 

Old Etna 

Paint Rock. . . . 
Poplar Lick. . . . 

Red Ash 

Rex Bed 

Richland 

Rich Mountain 
Sandstone Part- 
ing 

Sewanee 

Soddy 

Upper Dean. . . . 
Waldon Ridge. . 



2,320 


11.29 


2,260 


11.05 


2,640 


4.21 


2,340 


18.73 


2,290 


3.57 


2,140 


2.63 


2,420 


6.03 


2,610 


8.36 


2,570 


6.13 


2,230 


5.59 


2,590 


10.53 


2,370 


3.03 


2,380 


10.34 


2,460 


10.02 


2,580 


16.38 


2,290 


12.02 


2,580 


8.17 



2.77 
3.46 
0.92 
1.11 
1.39 
0.76 
1.74 
1.84 
1.13 
1.07 
0.92 
1.29 

1.26 
1.20 
1.16 
2.29 
0.92 



TEXAS 



Santa Tomas. 



2,580 



19.21 



1.98 



VIRGINIA 



No. 4 Bed 

"B" Bed 

Big Bed 

Big A., No. 2. . 
Big Townhill. . 

"C" Bed 

Clintwood 

Duncan 

Glamorgan 

Imboden 

Jawbone 

Kennedy 

Large Bed .... 
Little Townhill 



2,180 


6.58 


0.49 


2,420 


17.73 


2.21 


2,420 


19.89 


0.57 


2,320 


6.34 


0.60 


2,240 


11.84 


0.48 


2,210 


10.26 


1.40 


2,670 


3.26 


0.87 


2,160 


6.65 


0.88 


2,160 


5.86 


1.22 


2,420 


11.47 


1.56 


2,240 


19.86 


1.03 


2,190 


7.95 


1.09 


2,880 


20.19 


0.62 


2,440 


8.40 


0.56 



Little Bed 

Lower Banner. . . 
Lower Boiling. . . 

Meadow 

Milner 

Mohawk 

Pardee 

Pocahontas No.3 
Pocahontas No. 5 

Red Ash 

Small 

Splash Dam 

Upper 

Upper Banner. . . 



3,010 


21.29 


2,280 


6.37 


2,720 


8.74 


2,480 


12.92 


2,120 


5.89 


2,160 


3.49 


2,460 


8.04 


2,420 


4.26 


2,090 


5.19 


2,240 


5.96 


3,010 


42.98 


2,720 


5.77 


3,010 


29.72 


2,420 


6.43 



0.49 
0.72 
1.12 
0.62 
1.69 
1.32 
1.59 
0.54 
0.82 
0.64 
0.34 
0.65 
0.38 
0.67 



466 



FUEL 



Table 71. Fusibility of Ash from the Coals of the United States — Cont. 

WEST VIRGINIA 



Location and Bed 



Soften- 
ing 

Temp. 
Deg. 



Percent in 
Dry Coal 



of 
Ash 



of 
Sulphur 



Location and Bed 



Soften- 
ing 
Temp. 
Deg. 



Percent in 
Dry Coal 



of of 

Ash Sulphur 



No. 2 Gas 

Beckley 

Cedar Grove .... 

Coalburg 

Eagle 

Fire Creek 

Lower Freeport. . 
Lower Kittaning. 

Mahoning 

Middle Kittaning 
Pittsburgh 



2,750 


5.86 


0.88 


2,800 


4.76 


0.65 


2,610 


5.83 


1.07 


2,960 


8.80 


0.76 


2,940 


4.40 


0.77 


2,540 


6.60 


0.84 


2,090 


9.84 


3.14 


2,660 


7.64 


1.76 


2,160 


5.62 


1.89 


2,110 


10.93 


4.06 


2,170 


7.20 


2.24 



Pocahontas No. 3 
Pocahontas No. 4 
Pocahontas No. 5 
Pocahontas No. 6 

Redstone 

Sewell 

Sewickley 

Upper Freeport.. 

Welch 

Winif rede 



2,440 


4.70 


2,480 


6.31 


2,700 


6.23 


2,400 


2.88 


2,120 


6.96 


2,560 


3.93 


2,080 


9.51 


2,190 


6.17 


2,840 


7.41 


2,970 


8.44 



0.59 
0.64 
0.62 
0.70 
1.92 
0.72 
3.99 
1.97 
0.62 
0.83 



Avoiding Clinker. The following suggestions are offered by the Bureau 
of Mines: 

Use thin fires and keep the fuel bed level by placing fresh coal on thin 
spots. Do not level fire with rake or stir it with splice bar. 

Fire coal in small charges, especially if it contains much slack. This will 
prevent crust formation and the need of breaking it. 

Do not burn coal in the ashpit. Keep water in tight ashpits, otherwise 
blow in steam. In heating and decomposing, the steam will absorb heat as it 
passes through the grate, ash and fuel bed. 

Keep the ashpit doors open and regulate the draft by dampers. 

When the coal contains clinkering ash, an increase of the draft, states 
L. /. J affray, gives better combustion and reduces the slag. The air added 
through the fire keeps the temperature of the ash below the fusing point. 
Should clinkering continue, relief can be had, according to L. Rankin, by 
spreading over the grate a few shovelfuls of limestone crushed to the size 
of a walnut ; this should be done when the fire is banked or after it is 
cleaned. More heat may be lost by the frequent cleaning of the fire than 
because of its clinkering, especially with coals that fuse into large masses. 
Frequently the combustion is almost entirely stopped while the clinker is 
being removed. 

Storage of Coal 

COAL in a compact or solid mass, has the following approximate weights 
per cubic foot of space occupied : Anthracite, 85 to 95 lb. ; bituminous, 
70 to 80 lb. ; lignite, 65 to 75 lb. Peat weighs between 25 and 35 lb., while 
briquetted fuel weighs 40 to 45 lb. per cubic foot. Table 72 gives the approxi- 
mate weights of coals in storage. 

The variation in weight of different grades of coal is not due solely to 
the specific gravity of the solid coal. The quantity of surface moisture, the 
proportions of coarse and fine coal, and the amount of shaking or settling 
also influence its weight as delivered or as stored. Coals of high fixed carbon 
are relatively heavy, while increased ash content lowers the weight per cubic 
foot. The younger coals and those of high moisture content are relatively 
of low weight. 



FUEL 



467 





Table 72. 


Approximate Weights of 


Coals. 






Anthracite 


Name 


Bituminous 


Name 


Lb./cu. ft. 


Cu. ft./ton 


Lb./cu. ft. 


Cu. ft./ton 


Broken 

Stove 

Pea 

Buckwheat 


70 
65 
60 

55 


28 

31 
33 
36 


Lump 

Nut 

Slack 

Run of mine. . . 


60 
55 
50 
45 


33 

36 
40 

45 



Deterioration in Storage 

COAL undergoes a change in heat value and weight due to weathering 
when stored in the open, indoors or under water. Usually the volume 
and sometimes the weight is increased. Coal stored under fresh or salt water 
may retain from 2 to 12 per cent moisture, but its heat value is practically 
unchanged. Exposure of coal to the air, either in the open or under cover, 
reduces its heat value. The quantity of carbon and disposable hydrogen is 
diminished, while the quantity of oxygen and indisposable hydrogen is 
increased. 

Extensive experiments by S. W. Parr on Illinois coal showed that the 
most rapid loss in heat value occurred during the first ten days. After this 
the rate of loss diminished, although the loss continued indefinitely. The 
total loss in the open was substantially the same as in covered bins, ranging 
from 1 to 3 per cent after exposure for one year. 

Fine coal suffers a greater loss in heat value than do the larger sizes. 
The loss of volatile matter is negligible in its effect on heat value. After 
being exposed to air for one year, West Virginia slack lost less than 1 per 
cent in heat value ; run-of-mine only 0.5 per cent ; Pittsburgh run-of-mine 
0.4 per cent ; and Wyoming sub-bituminous about 3.5 per cent. This last 
coal deteriorated 5.3 per cent in heat value after an exposure to air for 2^ 
years. 

Coal in transit will lose in heat value because of oxidation of its new 
surface after mining. The loss increases with the hydrogen content, ranging 
from 0.1 per cent for semi-bituminous to 1.3 per cent for sub-bituminous 
and lignite. 



Spontaneous Combustion of Coal 

TN the storage of coal, spontaneous combustion must be provided against. 

■^ Anthracite coal is not subject to spontaneous combustion and can be 
safely stored in any quantity. Soft coal may ignite and disintegrate unless 
stored under water. 

Spontaneous combustion of coal is due to slow oxidation in an air supply 
sufficient to support the oxidation, but insufficient to carry away all the heat 
formed. The friability of the coal, or its tendency to break up into fine 
particles and dust, as well as its chemical nature, are the major causes of 
spontaneous combustion. 

Dust and small sizes of coal are dangerous in a coal pile containing 
larger-sized coal, because the resultant openings permit the flow of a mod- 
erate amount of air to the interior. The amount of volatile matter in the 
coal does not of itself increase the liability to spontaneous heating, and 
there is no assurance of safety in the storage of low volatile or smokeless 
coals. Pittsburgh run-of-mine has shown a greater tendency to spontaneous 




Finance Building, Philadelphia, Pa., equipped with Heine Boilers. 



FUEL 469 



combustion than have high volatile gas coals. Western coals with a high 
amount of volatile are usually liable, but this is due particularly to the high 
oxygen content. Such coals become heated readily by oxidation faster 
than the heat can be dissipated. 

The influence of moisture and sulphur on spontaneous combustion has 
not been definitely determined. The Bureau of Mines has not found a single 
instance of moisture causing heating, although laboratory tests by Richter 
show that moist coal oxidizes rapidly. While there are no conclusive data on 
the action of sulphur, experiments indicate that it is only a minor factor. 

According to the Bureau of Mines, the following precautions should be 
observed in storing coal : 

1. Do not pile in cones ; pile evenly not over 12 ft, and so that 
any point in the interior will not be over 10 ft. from an air cooled 
surface. 

2. If possible, store only screened nut coal. 

3. Keep out the dust as much as possible by reducing the handling 
to a minimum. 

4. Pile so that lump and fine sizes are distributed evenly, not 
allowing lumps to roll to the bottom and form air passages. 

5. Rehandle and screen after two months. 

6. Do not store near outside heat sources, even though moderate 
in degree. 

7. After mining, allow six weeks' seasoning before storing. 

8. Avoid alternate wetting and drying. 

9. Prevent air reaching the interior of the pile by avoiding inter- 
stices around timbers and brick work, or through porous bottoms, 
such as coarse cinders. 

10. Do not attempt to ventilate with pipes as they may do more 
harm than good. 
In practice coal that has been stored six to eight weeks and has even 
become heated will seldom again heat spontaneously if rehandled and thor- 
oughly cooled by the air. 

The drenching of the coal pile will not extinguish a fire, because the 
crust that forms over the fire prevents the water from reaching it. It is 
necessary to remove the coal from around the burning part and to spread 
out the coal before water can be used with effect. 

Briquets 

COAL dust, culm, slack and similar waste due to mining of the coals 
and low grade fuels unsuitable for transportation can be used as fuel 
by briquetting or pressing into solid blocks. Domestic experiments and the 
experience of foreign manufacturers indicate that briquetting increases the 
commercial value of low grade coals sufficiently to more than cover the 
cost of production. 

Undoubtedly on account of the low cost, briquetted fuel is used in 
European countries. In the United States, the difference in cost between 
steam sizes and slack is small and the cost of manufacturing the briquetted 
fuel is high, so that its use is limited to locomotive furnaces and to house 
heaters or stoves. However, tests by the U. S. Geological Survey with 
briquetted coal in hand-fired furnaces of Heine Boilers have repeatedly 
shown satisfactory economy, with no smoke. 

Briquets are generally machine made. Coal dust and small pieces of 
coal are mixed with a binding substance to hold the particles together, are 
heated, and are subjected to heavy pressure in molds. The fuel material 
is sometimes mixed with clay, rolled into balls by hand, and then air-dried. 
They are made in shapes and sizes. Fig. 213, weighing from 1 oz. to sev- 
eral pounds. Rectangular briquets measuring 6^4 by 5^2 by 4^ in. and 
having rounded corners, weigh about 7 pounds. Smaller briquets, of 6^^ by 
4J4 by lYz in. weigh about 4 lb. each. 



470 



FUEL 



,-^S 





















Fig. 213. Different Styles, 






-A - -i '. . . • 

■&s;--v'-" 











I 23456789 10 



APP>RO)aMATE SCALE &(YHS SIZES IN INCHES 

Shapes and Sizes of Coal Briquets. 



A? the coal resources of the countn- diminish, the economic importance 
of briquetted fuel will be better realized. Further development should 
also lead to methods for the recovery of valuable by-products from the 
coals used in making briquets. 

The size and shape of a briquet determine the extent of its use. Hea\y 
rectangular blocks are convenient for storage. According to /. E. Mills, 
the French Xa\'>- estimates the weight of briquets that can be stored in a 
given space as 10 per cent more than that of lump coal. The British 
Admiralty- reports a gain as high as 20 per cent. To hasten combustion large 
briquets are broken up when fed into the furnace. 

Stored briquets are not subject to spontaneous combustion or to notice- 
able weathering due to exposure. Briquets not over 2 lb. in weight are 
favored abroad. The most common forms are prismatic with round edges 
or ovoid shapes. These briquets are easily handled, cause little dust and 
minimum breakage. The rounded edges permit good air circulation and 
therefore thorough combustion. 

The properties of briquetted fuel depend largeh' upon the grade and 
amount of binder used with the coal mixture. The most common binder 
used, states C. L. Wright, is a pitch made either from coal tar or water-gas 
tar, although starch, lime and sulphite liquor are sometimes used. 

With the correct binder smokeless combustion can be expected. Other 
advantages of this fuel are regularity" in size, uniform condition of fuel-bed, 
no clinker, minimum, attention to fires, high heating value, high rates of 
combustion, small loss from breakage, and little weathering. 

Anthracite briquets have been made from coal dust mixed with drj- pitch. 
According to E. F. Loiscau, the pitch represents 10 per cent of the bulk of 
the briquet and is prepared from tar at h72 deg. by separating the volatile 
matter it contains. The fuel mixture is continuouslv heated by steam so 



FUEL 471 



as to maintain a temperature of 212 deg,, at which the pitch acts as a binder. 
It is then passed between rollers made of semi-oval molds, in which the 
briquets are formed. The pressed fuel, about the size of an egg, drops on 
to a belt conveyor ; this carries it to a screen in eight minutes, the briquets 
then being cool enough for handling and delivery. 

Carhocoal briquets are made in sizes ranging from 1 to 5 oz. and repre- 
sent about 72 per cent of the raw coal. As described by C. T. Malcolmson, 
the raw coal is first crushed and then distilled at a temperature of about 900 
deg., yielding gas, tar and "semi-carbocoal," which is rich m carbon. Pitch 
obtained from the tar is then mixed with the semi-carbocoal and formed into 
briquets. These are in turn distilled at a temperature of about 1800 deg., 
resulting in the recovery of additional coal-tar products and the production 
of the carbocoal fuel. The fuel is dense, uniform in size and quality, and of 
grayish black color. Anal3^sis shows from 1 to 3 per cent moisture ; 0.75 to 
3.5 per cent volatile matter ; 82 to 90 per cent fixed carbon and 7 to 12 per 
cent ash. It is said that carbocoal requires no greater draft than bituminous 
coal. 

Lignite briquets can be made without a binding material, according to 
the Bureau of Mines. Lignite briquets burnt in furnaces of steam boilers have 
proved equal to good Middle West bituminous coal. They will endure 
handling and resist weathering better than raw lignite, and manual labor is 
not required from the time the lignite is loaded into the mine car until the 
briquets are delivered to the consumer. 

The lignite after mining is crushed and screened and then dried to re- 
duce the high moisture content. Closed conveyors carry the powdered 
lignite to hoppers that feed the molds, where it is subjected to a pressure 
of about 20,000 lb. per sq. in. The heat developed during compression 
liberates the tarry matter from the material and cements the fuel. 

Lignite yields gas, ammonia, oils and tar on carbonizing. The residue 
can be made into briquets by the addition of a binding material. In one 
plant, states /. B. C. Kershaw, the ovens or retorts take a 10-ton charge of 
lignite and heat it for two hours at about 900 deg. The yield of by-products 
at this temperature include 10,000 cu. ft. of gas, 13 gal. of tar oil, and 2.5 lb. 
of ammonium sulphate per ton of lignite. After the distillation is completed 
the residue is mixed with pitch and other binders to form the briquets. 
Analysis of these lignite briquets shows 1.34 per cent moisture ; 7.6 per cent 
volatile matter ; 84.04 per cent fixed carbon ; 7.02 per cent ash, and a heat 
value of 14,000 B.t.u. per pound. 

Peat briquets are possible commercial fuel for steam boilers. The peat 
used abroad as a domestic fuel is not as rich in combined nitrogen as the 
peat of the United States. By gasification the latter will yield ammonia, tar 
and other chemical compounds of value. 

Peat produces a large amount of gas of good quality when consumed 
in a gas producer. The gas can be used in engines or for the firing of boil- 
ers. With by-product gas producers, sufficient ammonia can be recovered 
to pay for most of the operating costs, so that the gas and power it furnishes 
are practically free. 

Technical success, says F. P. Coffin, has been attained by several pro- 
cesses but commercial success in peat manufacture has not yet been demon- 
strated. Of the several plants that have at times operated in the United 
States, one uses a centrifugal pump for removing the peat from its bed. 
According to Win. Kent, the pump discharges into storage bins, and after 
some of the water in the peat has drained away, the material is further 
dried by exhaust steam and stack gases. When dry, the peat is reduced 
to powder, and conveyed to a press where it is compressed into regularly 
shaped blocks. The briquetted peat is clean and withstands handling as 
well as transportation. 




o 








<4-l 




CO 




U 




o 




a 




u 









U 




, 








o 




V 




u 




u 




V 








CU 




V 




j: 




<4-l 




Ui 




o 




*J 


. 


c 


CO 

u 


CO 


a; 






u 


o 


cj 


B 






^ 


u 


O 


G 


^ 


u 


CO 

6J3 


K 


C 


U-i 


u 





a 


, 


w 


PU 


-0 


Dd 


C3 
CO 


o 
in 


4> 


VO 


X, 


tn 


•4J 


CO 


fi 


4^ 


.1-1 


& 


03 


U 


0) 


a 




o 


o 




n 


>> 

c 


u 


ta 


c 


a 


V 


a 


ffi 



o 





CO 




ji 


a 
o 


H 






■*-> 




a 












a 




4J 




CO 




C 








04 




K 




00 




00 




CO 




CO 




(m 




o 




■M 




u 




CO 




a 





FUEL 



473 



Solid Fueis Other Than Coal 

yjH^ ODD fuel consists of sawdust, shavings or other refuse produced in 
^^ quantity, as in wood-working plants and saw mills. Cord wood is 
used to a limited extent, when timber is plentiful and other fuels expensive. 
Wood, of course, is used in starting coal fires. 

Table 73. Weights and Compositions of Air-Dried Woods. 



Wood 



Lb. per 
cu. ft. 



Lb. in 
1 cord 



H. 



N 



Ash 



Heat 
Value, 

B.t.u. 
per lb. 



Ash... 
Beech . 
Birch . . 
Elm... 

Oak... 
Pine . . . 
Poplar. 
Willow 



46 
43 
45 
35 



3,520 
3,250 
2,880 
2,350 



49.18 
49.36 
50.20 
48.99 



6.27 


43.91 


0.07 


6.01 


42.69 


0.91 


6.20 


41.62 


1.15 


6.20 


44.25 


0.06 



0.57 
1.06 
0.81 
0.50 



5,420 
5,400 
5,580 
5,400 



52 


3,850 


49.64 


5.92 


41.16 


1.29 


30 


2,000 


50.31 


6.20 


43.08 


0.04 


36 


2,130 


49.37 


6.21 


41.60 


0.96 


25 


1,920 


49.96 


5.96 


39.56 


0.96 



1.97 
0.37 
1.86 
3.37 



5,460 
6,700 
6,660 
6,830 



Freshly cut wood contains about 45 per cent of water by weight. After 
air-drying the moisture content is 15 to 25 per cent. The average heat value 
of dry wood is about 7700 B.t.u. per pound. The weights and com- 
positions of air-dried wood are given in Table I'i. As fuel, 1 lb. of 
wood is assumed to equal 0.40 lb, of coal, or 1 lb. of coal equals 2^ lb, of 
wood. Measuring in bulk, 2 cords of wood are considered the equal of 1 ton 
of coal. Sometimes 1 lb. of wood is said to give an evaporation of 6 lb. of 
water from and at 212 deg., which represents a heat value of 5794 B.t.u. 
per pound. By weight, shavings, sawdust and refuse lumber have the same 
heat value as the original wood. 

Charcoal is made by heating wood in a closed vessel. Distillation begins 
at about 400 deg., leaving a residue of common black charcoal. Other grades 
of charcoal are obtained at higher carbonizing temperatures. The wood 
melts, and at about 620 deg. yields a mass similar to soft coal coke. At 
temperatures over 2000 deg. a black dense solid charcoal is formed. 

Wood will yield about 18 per cent charcoal and 82 per cent volatile matter 
by weight at high temperature, and 68 per cent charcoal and 32 per cent 
volatile at low temperature. The carbon content varies then from 85 to 55 
per cent. The heat value is generally about 11,000 B.t.u. per pound. Char- 
coal absorbs moisture rapidly up to 15 per cent. It is seldom used in boiler 
practice except when it is a by-product, as in the manufacture of wood alcohol 
or turpentine. 

Coke is the solid substance remaining after coals are distilled in retorts 
or partly burned in ovens. The bituminous coals are used extensively, al- 
though lignite and peat offer commercial possibilities. In gas retorts, a large 
yield of gas of high illuminating value is desired, so that the coke is a by- 
product. In beehive coke ovens high-grade coke is produced for use in 
metallurgical processes. In by-product coke-ovens, good coke, a large coke 
yield or else gas and chemical by-products may be desired. The coke 
yield varies between 35 to 90 per cent of the weight of coal. Cokes are 
generally rough and may be dense and soft, or porous and hard. The color 
varies from silvery, light gray to dark gray and black. They readily 
attract and retain moisture and if not properly protected may contain 20 



474 



UEL 



per cent by weight. Coke bums without flame or smoke and makes an in- 
tense tire when forced. The heat value is between 12,000 and 14,000 B.t.u. 
per pound. Analysis gives an average of 1.3 per cent volatile matter ; 88 per 
cent fixed carbon ; 0,8 per cent sulphur ; 1.5 per cent moisture ; and 8.4 
per cent ash. The average weight of solid coke is about 45 lb. per cubic 
foot. Heaped coke weighs about 30 lb. per cubic foot, or 75 cubic feet to 
the long ton. Coke generally costs as much as coal, so that it is not used 
to anj' extent as a boiler fuel. 

Coke breeze consists of the line particles left when the coke is drawn 
from the ovens, or of the screenings from coke prepared for blast furnaces. 
It represents about 2 to 2^2 per cent of the coal originally used in the coking 
process. Generally, it is considered as waste, but by burning coke breeze 
under boilers, its fuel value can be utilized. 

Com has been used as fuel when the crop was plentiful and the price 
low. At 15 cents a bushel corn would be as cheap a fuel as coal at about 
S8 per ton. It is sometimes used as an emergency fuel in grain-growing 
localities. Boiler tests by C. R. Richards showed that bituminous coal gave 
1.9 times as much heat per pound as corn on account of the difference in 
heat value of the fuels. Calorimeter tests place the heat value of corn and 
cob at about 8000 B.t.u. per pound, the cob alone at 7500 B.t.u., and dry 
corn at 9000 B.Lu. Corn weighs about 56 lb. per bushel. 

Strazv, used in som.e localities as fuel, consists of the stems or stalks of 
grain. Its composition is about 36 per cent carbon ; 5 per cent hydrogen ; 
38 per cent oxygen; 0.5 per cent nitrogen; 15.75 per cent moisture; and 4.75 
per cent ash, which gives a heat value of 5411 B.t.u. per pound. Dr>- straw 
will average from 5600 to 6700 B.t.u. per pound. Straw when compressed 
weighs about 7 lb. per cubic foot. 

Tan bark is the fibrous portion, known as spent tan, which is left from 
ground bark emploj-ed as a leather tanning agent. The raw bark is usually 
air-dried oak or hemlock but in the process it absorbs sufficient moisture to 
make the spent tan weigh more than twice the raw material, two-thirds of 
this weight being water. The waste heat of the chimney gases can be used 
for dr\-ing the fuel. 

Fig. 214 gives heat values of tan bark for different moisture contents, 
derived from Table 74. The net heat value cannot be measured directly, so 
that the total calorific value should be determined by combustion in a fuel 
calorimeter. At best, the useful heat of a liquid, gaseous or wet fuel, can be 
determined only approximately, for it involves the ultimate analysis and 
assumptions depending upon operating conditions. 



Table 74. Calorific Value of Tan Bark with various Percentages of Moisture, 





B.t.u. 

per Lb. 

Wet 

Tan. 


Losses of Heat due 




Net Heat 
Value, 
B.t-u. 


Efficiency, 
Per cent 


Lb. Evap. 
per Lb. 


Moisture 


Moisture 


H 


1 

in Fuel Heating Air 


Wet 
Tan. 


0.20 
0.30 
0.40 


6,336 

5,544 
4,752 


261 
392 

^ T 1 


564 
493 

423 


1,446 
1,266 

1.085 


4,065 
3,393 

2.772 


64.2 
61.2 

57.3 


4.19 
3.50 

2.81 


0.50 
0.60 
0.70 
O.SO 


3,960 
3,168 
2,376 
1,584 


653 

784 

914 

1,045 


352 
282 
211 
141 


904 
723 
542 
362 


2,051 

1,379 

709 

36 


51.8 

43.5 

29.8 

2 5 


2.11 
1.42 

0.73 
. 03 



Composition of dry tan bark a^umed to be C, 0.50; H, 0.06; O, 0.40; N and Ash, 0.04. Heating 
value bf Dulong's formula 7,920 B.t.u. per pound. Exit gases are assumed to be at 600 deg. Fabr. 



FUEL 



475 



6000' 




-^ 


^ 


'* 




" 












~ 
















■" 


■ 




n 




























■ 










■ 




■■ 






.. 


■■ 




















































































































































































































>» 








































































































>»^ 


^ 










































































































■«« 




























































































"ic 






































































































OS 






























































































































■^ 








































































































" 


V 


^ 










































































































■> 


































































^ 


l^ 




































' 


». 












































































































■> 


























































"«? 
















































•^ 












































































































> 
















































•^ jLM) " 
























































■^ 


•> 












































>? 
































































>., 








































































































">>. 




































"^ 








































































•»-. 








































































































"■«, 












































































































^. 






















t^ 


















































































■■»^ 






































































































"^ 


r^. 


















b 


































































































































































































h. 


, 








































































































■>« 






^ 




































































































^, 


S 






































































































^ 






































































































9nn/) . 






























































































































































































































































































































































































































































































































1000'. 







































































































20 



3C 40 50 60 

Moisture in Fuel, Percent 

Fig. 214. Heat Value of Tan Bark. 



70 



80 



Dry tan bark consists of about 50 per cent carbon; 6 per cent hydrogen; 
40 per cent nitrogen ; and 4 per cent ash, giving a heat value of 8000 B.t.u. 
per pound. Dry tan bark with 15 per cent ash has a heat value of about 
6100 B.t.u. ; and with 1.5 per cent ash, about 9000 B.t.u. per pound. Wet 
tan bark, as used for boiler firing, has a heat value of about 5500 B.t.u. 
per pound with 30 per cent moisture; and 3500 B.t.u. with 60 per cent 
moisture. An evaporation from and at 212 deg. of 2 to 3 lb. of water 
per pound of wet fuel can be expected in specially designed furnaces. 

Bagasse, or megass, that part of the sugar cane remaining after the ex- 
traction of the juice, is widely used as fuel for boilers on sugar plantations. 
The refuse resulting from the treatment of the raw cane by the sugar mill 
rolls is known as "mill bagasse," while the product remaining after a series 
of soaking processes of the raw chopped cane is known as "diffusion bagasse," 
The fuel value of bagasse depends upon the amount of woody fiber it 
contains and upon the amount of combustible matter, such as sucrose, 
glucose and gum, retained in the liquid. Louisiana bagasse, according to 
E. C Freeland, consists of about 40 per cent fibre, 7 per cent sucrose and 
other constituents, the remaining 53 per cent being water. Bagasse obtained 
from tropical cane, according to L. A. Be cud, contains Z7 to 45 per cent 
woody fiber ; 9 to 10 per cent combustible ; and 46 to 53 per cent water. 
The composition of dry bagasse ranges between 43 and 47 per cent carbon ; 
5.4 and 6.6 per cent hydrogen ; 45 and 49 per cent oxygen ; and 5 and 3 
per cent ash. Its average heat value as determined by test is 8300 B.t.u. 
per pound. Owing to the usual moisture content of the fuel as fired, its 
heat value then is only 400O B.t.u. or less. One pound of the fuel will 
evaporate about 2 to 3 lb. of water from and at 212 deg. By utilizing 
waste gases and drying the bagasse before firing, better results can be ob- 
tained. The fuel yield from sugar cane can be taken as 25 per cent. One 
ton of cane as ground will therefore give 500 lb. or more of wet bagasse. 

Table 75 gives the calorific values of diffusion bagasse of varying per- 
centages of moisture. 

Table 76 gives the calorific value of one pound of mill bagasse at dif- 
ferent extractions, based upon a cane of 10 per cent fiber and juice of 15 
per cent total solids. 



476 



FUEL 




o 
O 

OS 
O 



CO 

c8 



at 



<U O 

o lu 

^ o 

ffi . 

7^ ro 



V-l -.4 

03 

o ^ 
CO 



.5 & 
u o 

ml 

(4-1 
O 

X 

o 
o 



FUEL 



477 



Table 75. Fuel Values of One Pound of Diffusion Bagasse at Various 

Degrees of Moisture. 



Mobture in Bagasse, 
Per cent. 


Heat Developed per 

Pound of Bagasse, 

B.t.u. 


Heat Available per 

Pound of Bagasse, 

B.t.u. 


Number of Pounds 

of Bagasse 

Equivalent to 

1 Lb. of Coal of 

14,000 B.t.u. 




20* 

- 30 


8,325 
6,660 

5,827 


8,325 
6,420 
5,468 


1.68 

2.18 
2.56 


40 
50 

60 


4,995 
4,162 
3,330 


4,516 
3,563 
2,611 


3.10 
3.93 
5.41 


70 

75 


2,497 
2,081 


1,658 
1,183 


8.44 
11.90 



Table 76. Fuel Values of One Pound of Mill Bagasse at different Extrac- 
tions upon Cane of 10 per cent Fiber and Juice of 15 per cent Total Solids. 



c 
o 




Fibre 


Sug 


ar 


Molasses 


-a 
"3 


1 
0. . 

> a 




CO 

OJ OJ 
^ 


c 

E-" 


.2 


0) 




52 




CO 

CO 




0. 


Is 
Is 

4J O 


3 
"o 

0) K 


be 
a 

m 
.2 

c 

0) 


;> . 


c4 

m 

c 
c 


1 


CS 

tc 

m 
.s 


3 
I 


> 

Q 
a 

0) 


-Si 

a; <c 
P55 


> 

< 


CO 

CO • 


ca 3 


O bO 


w a 


t> 


— 3 


V 


-H 3 


u 


— 3 


"eS 3' 


-e '3< 3 


■e 3 


«r?2 


^- c« 








fe pq 










H fq 




W pq 




6^ 


90 


0.00 


100.00 


8,325 










8,325 




8,325 


1.68 


119 


85 


28.33 


66.67 


5,550 


3.33 


240 


1.67 


116 


5,900 


339 


5,561 


2.52 


119 


80 


42.50 


50.00 


4,162 


5.00 


361 


2.50 


174 


4,697 


509 


4,188 


3.34 


120 


75 


51.00 


40.00 


3,330 


6.00 


433 


3.00 


209 


3,972 


611 


3,361 


4.17 


120 


70 


56.67 


33.33 


2,775 


6.67 


482 


3.33 


232 


3,489 


679 


2,810 


4.98 


120 


65 


60.71 


28.57 


2,378 


7.15 


516 


3.57 


248 


3,142 


727 


2,415 


5.80 


121 


60 


63.75 


25.00 


2,081 


7.50 


541 


3.75 


261 


2,883 


764 


2,119 


6.61 


121 


55 


66.12 


22.22 


1,850 


7.78 


562 


3.88 


270 


2,682 


792 


1,890 


7.40 


121 


50 


68.00 


20.00 


1,665 


8.00 


578 


4.00 


278 


2,521 


815 


1,706 


8.21 


122 


45 


69.55 


18.18 


1,513 


8.18 


591 


4.09 


284 


2,388 


833 


1,555 


9.00 


122 


40 


70.83 


16.67 


1,388 


8.33 


601 


4.17 


290 


2,279 


849 


1,430 


9.79 


123 


25 


73.67 


13.33 


1,110 


8.67 


626 


4.33 


301 


2,037 


883 


1,154 


12.13 


124 


15 


75.00 


11.77 


980 


8.82 


637 


4.41 


307 


1,924 


899 


1,025 


13.66 


124 





76.50 


10.00 


832 


9.00 


650 


4.50 


313 


1,795 


916 


879 


15.93 


126 



Fig. 215 gives the heat value of both "diffusion" and "mill" bagasse, cor- 
responding to Column 2 of Table 75 and Column 9 of Table 76. 



Heat Value of Wet Fuels 

"T^HE useful heat liberated by fuels fired wet is lower than the total heat 
-'- value determined by calorimeter tests. The calorific power, as fired, of 
green wood, tan bark and bagasse, is termed the gross heat value. By de- 
ducting from this gross value the heat required to evaporate the moisture 
and raise it to the temperature of the gases leaving the boiler, the net heat 



478 



FUEL 




30 4C so 

Moisture in Fue/, Percenf 

Fig. 215. Heat Value of Bagasse. 

value absorbed by the boiler water is obtained. Therefore, a dr>' sample 
having a total of 7000 B.t.u. per pound by calorimeter test will have a gross 
heat value of 5600 B.tu. per pound, if it contains 20 per cent moisture. 

To compute the net heat value of wet fuels, the following formula can 
be used : 

h. L=(9H+ JV) X [ (212 - -f 972] - [0.48 (h - 212) ] (59) 

ill which h. 1. is the B.t.u. lost per pound; H is the hydrogen content; 17 
the water; t and fi are the temperatures of the air supply and the chimney 
gases. The result is the heat lost in the superheated steam_ formed by the 
combustion of the hydrogen and from the water in the wet fuel. 

If green wood contains 6 per cent hydrogen and 24 per cent water as 
fired, and the air supplied for combustion is at 72 deg., resulting in a stack 
temperature of 462 deg., the loss is: 
(9 X 0.06 + 0.24) X [ (212 - 72) H- 972] ^ [0.48 (462 - 212) ] = 987 B.t.u. 

Assume that this wood sample has a heat value of 6987 B.t.u. by calorimeter 
test. The net heat value is found by deducting the loss due to hydrogen and 
water, which gives 6000 B.t.u. per pound for steaming purposes. 



Liquid Fuels 

FUEL oil consists practically of petroleum or of its residue after the rnore 
volatile oils have been removed. The petroleum or crude oil is a 
viscous mineral oil varying in color from light brown through shades of 
green to black. The specific gravity is generally between 0.80 and 0.98. 
corresponding to 45 and 12 deg. Baume. respectively. 

Fuel oil at 10 deg. Baume has a specific gravit}- of 1.00. the same as that 
of water. The gravit>- of oil is usually measured on the Baume scale. This 
can be converted by the following Bureau of Standards formula, for liquids 
lighter than water : 

. ^ . 140 (60) 

Specific Gravity = 



130 - deg. Be 



Deg. Baume = 



140 
Spec. Grav, 



— 130 



(61) 



FUEL 



479 



Crude oil is a mixture of hydrocarbons that often contain a small per- 
centage of sulphur, oxygen and nitrogen. It can be distilled into gasoline. 
benzine, kerosene and other oils, which differ considerably physically and 
chemically, depending upon the locality, the source of supply, and upon 
the treatment or distillation process. After the kerosene has been run off, 
the oils remaining, of from 12 to 25 deg. Baume, are available as fuel for 
steam boilers. 

Gasoline is a petroleum product of about 74 to 64 deg. Baume. Benzine 
is a distillate of about 55 deg. Baume, while kerosene ranges from about 
48 to v35 deg. Baume. However, the high price of these lighter distillates 
prevents their use as a boiler fuel. 

Oils are classified by their flash point, the temperature at which they 
give off inflammable vapors ; viscosity, the tendency of the oil particles to hold 
together, thus retarding the flow ; moisture, in the form of an emulsion in 
the heavier oils ; sulphur, which produces obnoxious gases and has a cor- 
roding effect if condensed on boiler tubes and stack; density; and heat value. 
The properties of fuel oils from different localities are given in Table 
77, by C. E. Lucke. 



Table 77. Composition land Heat Value of Oil Fuels. 





Deg. 
Baume 


Ultimate analysis, per cent 


Heat 
value. 


Kind 


C. 


H. 


O+N. 


s. 


B.t.u. 
per )b. 


California fuel oil 

California crude 

Kansas crude 


14.93 
16.24 
31.67 
38.89 
23.18 
21.25 
21.56 
36.47 


81.52 

86.30 
85.40 
85.00 
86.10 
83.26 
84.60 
84.30 


11.61 
16.70 
13.07 
13.80 
13.90 
12.41 
10.90 
14.10 


6.92 


0.55 
0.80 


18,926 
21,723 
20,345 


Ohio crude 


0.60 

'"3;83" 
2.87 
1.60 


0.60 
0.60 
0.50 
1.63 


20,752 


Pennsylvania crude. . . 

Texas fuel oil 

Texas crude 

West Virginia crude. . . 


20,949 
19,654 
18,977 
20,809 



The heat value of oil can be determined accurately by calorimeter test. 
An approximate method proposed by /. N. LeConte gives the value, free 
from moisture, as 17,680 + (60 X deg. Be) B.t.u. per pound. 

Another method utilizes the Dillon" formula: 



B.t.u. ^ 14,544 C + 62,028 /'i/ ^ ) + ^050 .S" 



(62) 



in which C is carbon, H is hydrogen, is oxygen and S is sulphur, as ob- 
tained from the ultimate analysis. This formula gives a heat value of 
about 5 per cent higher than that of California oils, as determined by calo- 
rimeter. Fig. 216 shows other heat values. These indicate that per pound the 
lighter oils have a higher calorific value than the heavier fuels, but a lower 
value per gallon. A barrel of heavy petroleum will therefore have a higher 
heat value than a barrel of lighter oil. 

The average California oil has a specific gravity of about 0.96, which 
corresponds to 15.16 deg. Baume at a temperature of 60 deg. The average 
weight of a gallon of oil is 8.03 pounds. As it usually comes in barrels of 
42 gal., the average weight of a barrel of fuel oil is ZZ7 pounds. The 
heat value is about 18,700 B.t.u. per pound, which should easily give an 
equivalent evaporation from and at 212 deg. of about 14.5 lb. of water per 
pound of fuel. 




Peoples Gas, Light 8b Coke Co., Chicago, Ills., operating Heine Boilers, 



FUEL 



481 




'iBZOO ^'^ *°° 18500 ^°° ^°° ^'^ ®°° 19000 "'^ ^°° '""^ ''°° 19500 



B.t.u. per Pgund 

Fig. 216. Heating Value of Fuel Oil. 



Coal tar is a by-product of coking processes. Its commercial value 
usually prevents its use as a fuel. This black, viscous liquid must be heated 
and strained before it can be used. The coal tar yield is from 4^ to 6j/4 
per cent of the weight of the coal used in gas or coke manufacture. The 
specific gravity is about 1.25, so that a gallon weighs 10.4 pounds. It is 
lower in hydrogen and higher in carbon than petroleum, an ultimate analysis 
showing 89.21 per cent carbon; 4.95 per cent hydrogen; 1.05 per cent nitrogen; 
4.23 per cent oxygen ; 0.56 per cent sulphur ; and a trace of ash. Coal tar has 
a heat value of about 15,800 B.t.u. per pound. 

Tar oils include pitch, creosote, anthracene and other residuum from 
distillation. Oil tar produced in gas apparatus has a specific gravity of 1.15, 
is less viscous than coal tar, and can be handled much like other fuels. Its 
composition is 92.7 per cent carbon; 6.13 per cent hydrogen; 0.11 per cent 
nitrogen; 0.69 per cent oxygen; 0.37 per cent sulphur; and a trace of ash. 
giving a heat value of 17,100 B.t.u. per pound. 

Colloidal fuel was developed by the Submarine Defense Association 
to meet war conditions. It is an emulsion of powdered solid fuel and oil 
fuel. A so-called fixateur is used to stabilize the elements of the mixture 



482 FUEL 

that have different specific gravities, and thus maintain a homogeneous 
product. Most oils in their natural state can be mixed with pulverized 
solids to make the smokeless colloidal fuel. Dried and pulverized bituminous 
and anthracite coals can be used, as can lignite, peat coke, charcoal or wood, 
so long as two-thirds of the dn.- solid fuel is combustible. 

The colloidal fuel is fired with the same equipment used for oil burning. 
A marine boiler test gave an equivalent evaporation of 13.6 lb. of water 
per pound of colloidal fuel at an efficiency of 76.8 per cent, while straight 
Mexican oil gave an equivalent evaporation of 13.97 lb. of water per pound 
of oil fuel at an efficiency of 73.32 per cent. With coal of 13.500 B.tu. 
per pound and crude oil of 18,200 B.t.u. per pound, the colloidal fuel has 
a heat value of 17.000 B.t.u. per pound, with 25 per cent solid fuel in 
suspension ; and 16.300 B.t.u. per pound with 40 per cent of solids in the 
mixture. It is possible to combine 45 per cent oil. 20 per cent tar and 30 
per cent powdered coal and still obtain a stable colloidal fuel that can be 
stored for a month or more without the solids settling. With such mixture 
it is said at least 50 per cent of the oil fuel now used can be saved, and equal 
if not greater heat value per barrel obtained at a lower cost. 

Gaseous Fuels 

IX ga? fuels each constituent has a known heating power. The total 
heat value of a cubic foot of gas can be determined by multiphnng the 
fractional constituents and the corresponding heating powers per cubic foot, 
and by adding the products. The low heat values are given by C. E. Lucke 
as follows : 

Gas B.t.u. per cu. ft. 

Hydrogen _ _ 292 

Methane -_ - _ - _.. 959 

Ethjlene — - 1595 

Benzine (or illuminants contained) „ 3795 

Carbon monoxide„ — 341 

Natural gas is often held at high pressure in huge natural, underground 
reser\-oirs that are tapped by sinking wells. The gas is piped and distributed 
over long distances, and delivered at working pressures of 2 to 8 ounces. 

The principal combustible components of natural gas are methane (marsh 
gas) and hydrogen. The incombustible gases are carbon dioxide, nitrogen 
and ox\gen. Table 78. compiled bj* G. A. Burrell, gives the average heat 
value and the composition for different samples. 

Arti/ia'ul gases are made principally from coal or oil. Natural gas 
costs 10 to 30 cents per 1000 cu. ft., while coal and water gases cost $1 or 
more. With coal at S5 per ton, producer gas will deliver 35,000 B.t.u. for 
one cent, while natural gas at 20 cents gives 50.000 B.t.u. for one cent. 

The compositions and heating values of gas fuels are compared in Table 
79. Owing to the variations in heat values, different quantities of gas are 
required to generate one boiler horsepower. 

Junker Gas Calorimeter 

THE heat value of gaseous fuels is generally determined with the Junker 
Gas Calorimeter illustrated in Fig. 217. 

This instrument consists of a vertical cylindrical water chamber contain- 
ing vertical tubes, ^rhich is heated bj* the gas burned in a Bunsen lamp 
beneath. The products of com.bustion pass upward through a combustion 
chamber and downward through the tubes, while the water passes in at the 
bottom and out at the top in a continuous current. The quantity of gas is 
measured by a gas meter, and the quantity of water by collecting the overflow 



FUEL 



483 



Table 78. Properties of Natural Gas. 
(G. A. Burrell, Nat. Gas A.ssn. of America, May, 1914) 





Volumetric Composition, Per cent 


Higher 
Heating 

Value 
B.t.u. per 

Cu. Ft. 

32° F and 

29.92 in. 


Specific 


Location of Wells 


Carbon 

Dioxide, 

CO2 


Oxygen 
O2 


Nitrogen 

N2 


Methane 
CH4 


Ethane 
C2H2 


Gravity, 
Airz=l 


Armstrong Co., Pa. 
Osage Co., Okla. . . 
Kiefer, Okla 


0.05| 0.0 

1.10: 0.0 

2.40I 0.0 


1.45 
4.6 

1.8 


81.6 
94.3 
64.1 


16.9 

0.0 

31.7 


1,184 
1,004 

1,272 


0.64 
0.58 
0.74 


Barron Co., Ky. .. . 

Barron Co., Ky 

Moab, Utah 


2.5 
2.6 
3.6 


0.0 
0.0 

0.0 


1.3 
5.1 
5.6 


23.6 
44.1 
90.8 


69.7 

48.2 

0.0 


1,548 

1,367 

967 


0.91 
0.84 
0.61 


Moab, Utah 

Northwestern Ore . 
Crawford Co., Pa. . 


3.5 
3.0 
0.0 


0.0 
0.0 
0.0 


6.5 
0.9 

2.3 


90.0 

96.1 

6.6 


0.0 

0.0 

91.1 


959 
1,023 
1,766 


0.62 
0.58 
1.01 


Northwestern Ore . 
Tillamook, Ore. . . . 
Stillwater, Nev. . . . 


0.5 
0.1 
1.3 


0.0 
0.0 
0.0 


12.5 

97.9 

3.1 


87.0 

2.0 

95.6 


0.0 
0.0 
0.0 


927 

21 

1,018 


0.60 
0.96 
0.58 


Clarion Co., Pa.. . . 

Forest Co., Pa 

Clarion Co., Pa.. . . 


0.0 
0.0 
0.0 


0.0 
0.0 
0.0 


1.1 
1.0 
1.7 


96.4 
70.8 
80.5 


2.5 
28.2 
17.8 


1,073 
1,279 
1,189 


0.57 
0.70 
0.65 


Butler Co., Pa 

Kings Co., Cal .... 
Greybull Field, Wyo 


0.0 

30.4 

0.2 


0.0 
0.0 
0.0 


0.9 
2.4 
0.8 


53.3 
66.2 
81.7 


45.8 

1.0 

17.3 


1,420 

724 

1,192 


0.78 
0.85 
0.64 


Casing head gas. . . 
McKean Co., Pa. . 


0.0 
0.5 
0.0 


0.0 
0.0 
0.0 


1.3 
3.1 
1.0 


51.5 
64.1 
86.0 


47.2 
32.3 
13.0 


1,427 
1,282 
1,159 


0.77 
0.68 
0.59 


Caddo Parish Field, 

La 

Park County, Okla. 


0.9 0.0 
0.0 0.0 


1.5 
1.8 


97.6 
94.4 


0.0 
3.8 


1,039 
1,076 


0.57 
0.59 


Bradford, Pa 

Nortonville, N. D.. 
Schulto Field, Okla. 


0.0 
1.3 
0.5 


0.0 
0.0 
0.0 


8.9 

13.6 

1.5 


18.9 
85.1 
76.4 


72.2 

0.0 

21.6 


1,534 1.00 

907 0.62 

1,215 0.67 


Casing head gas 
used for produc- 
tion of gasoline. . 


0.0 


0.0 


3.3 


78.7 


18.0 


2,424 


1.38 


From Pittsburg gas 
supply 

From Columbus gas 
supply 


0.0 
0.0 


0.0 
0.0 


1.2 
1.6 


79.2 
80.3 


19.6 
18.1 


1,208 
1,193 


0.65 
0.64 



Table 79. Composition of Gas Fuels, by Percentages. 



Fuel 


Combustible — by Volume 


Incombustible-by Volume 


Heat 
Value, 
B.t.u. 




Hydrogen 


Methane 


Ethylene 


Carbon 
Monoxide 


Carbon 
Dioxide 


Oxygen 


Nitrogen 


per 
cu. ft. 


Natural gas 

Coal gas 

Water gas 


1.7 
39.78 
21.8 


94.16 
45.16 
30.7 


0.30 
6.38 
12.9 


0.55 
7.04 
28.1 


0.29 
1.08 
3.8 


0.30 
0.06 
0.5 


2.80 
0.50 
2.2 


1,000 
730 
700 


Coke oven gas.. . 
Blast furnace gas 
Producer gas. . . . 
Oil gas 


53.2 
3.0 
2.81 

32.0 


35.0 


2.0 


6.0 
27.5 
14.34 


2.0 
10.0 
10.5 


' 'o!r 

0.5 


2.0 
59.4 
66.7 

3.0 


620 
100 


5.56 
48.0 


"l6"5' 


110 
850 












u 
Q 

c 

o 

■i-t 

C 



o 
o 

x: 
o 






c 

V 

U 



o 



CO 

c 

C3 
u 

c 



o 



3 
O 



FUEL 



485 




Fig. 217. The Junker Gas Calorimeter. 

discharged from the apparatus. Thermometers are inserted at the points of 
entrance and exit. The heat of combustion of a cu. ft. of gas is determined 
by multiplying the rise of temperature in deg. F. by the weight of water 
in lb., and dividing the product by the volume of gas in cu. ft. The result 
thus found after being corrected for moisture and reduced to the equivalent at 
32 deg. and 14,696 lbs. per sq. in., is what is termed the "higher value," and 
this is the value, unless otherwise stated, which is generally employed. 

The ''low value" is obtained by multiplying the weight of the con- 
densed vapor resulting from the combustion, expressed in lb., by the total 
heat of atmospheric steam above the temperature of the condensed vapor, 
dividing the product by the volume of the gas in cu. ft., and subtracting the 
quotient from the higher value. 



Heat Value of Liquid and Gaseous Fuels 

THE heating power of a fuel, as used in calculating boiler trials, is the 
value determined by calorimeter test. Some fuels contain hydrogen, and 
others moisture, thus reducing the heat available for steam. 

Most liquid fuels and some gases contain a high percentage of hydrogen. 
Their calorific power as determined by calorimeter test is called the "high" 
heat value, while the available heat is known as the "low" heat value. 
The difference between the two is equal to the latent heat of steam formed 



486 FUEL 

by the burning of the hydrogen, which cannc: be absorbed by the wa:er in 
the boiler. As hydrogen combines with eight times its weight of oxygen, 
the result is 9 lb. of water for the combustion of 1 lb. of hydrogen. ' The 
latent heat of steam being 97U B.t.u. per pound, this combustion represents 
a total of 8745 B.t-u. per pound of hydrogen. Deducting this from 60,626 
B.Lu., the high heat value of hydrogen, gives 51,1^ B.Lu. as the low 
heat value per pound of hydrogen. On a volumetric basis the high heat 
value of hjdrogen can be taken as 340 B.t-u. per cubic foot and the low 
heat value as 290 B.t.u., leaving 50 B.t.u. per cubic foot that is not absorbed 
by the boiler water. 

If a calorimeter test gives the high heat value of oil as IS ': B.tu. 
per pound and the fuel contains 10 per cent hvdrogen, the:. :'.'.- ! ei: 

value is 18,500 — (0.10 X 8745) = 17,625 B.t.u. per pound ap;:-::-i.:-:: . 

If a sample of gas fuel containing 20 per cent hydrogen by volume has a 
high heat value of 710 B.t-u. per cubic foot as determined by calorimeter, 
then the low heat value is 710 — (02 X 50) =700 B.t.u. per cubic foot 

Buying Fuels Under Contract 

' I HE purchase of fuels under contract and specification involves expense in 
-»• sampling and analysis, but many engineers believe the advantages gained 
are worth the cost. Large consumers of coal and oil have adopted the con- 
tract and specification method, because it guarantees economy when quaUty 
and price are considered. Power reports a saving of S20.000 in the coal 
bills of 18 plants, the fuel having been tested at a central laboratory at a 
cost of $1,500 for the year. 

Specifications insure a more uniform grade of fuel than can be other- 
wise obtained. Boiler plant operation can be studied more carefully and 
adjustments made to secure the highest efficiency with the grade of fuel 
delivered. However, sampling and analyzing are expensive. Fuel contractors 
hold that many specifications are unreasonable, and sometimes add 5 to 10 
per cent to the price to cover contingencies. 

Specifications for Coal 

THE following specification for the purchase of coal on a heat value basis 
is given by /. E. Woodwell, as typical of central power station practice : 
A. The company agrees to furnish and deliver to the consumer. 

, at such times and in such 

quantities as ordered by the consumer for consumption at said premises 
during the term hereof, at the consumer's option, either or all of the kinds 
of coal described below; said coals to average the following assays: 

Coal of size passing through 
screen having circular 
perforation in diam. . in. in. in. 

Coal of size passing over 
screen having circular 
perforation in diam in. in. „ in. 

Moisture in coal as de- 
livered 9c % - % 

Ash in coal 
as deUvered % % % 

Heat value per pound of 
dr\- coaL B.Lu. B.t.ii- B.tu. 

From following count}* 

From following state 



FUEL 487 

Coal of the above respective descriptions and specified assays, not aver- 
age assays, to be hereinafter known as the contract grade of the respective 
kinds. 

B. The consumer agrees to purchase from the company all of the coal 
required for consumption at said premises during the term of this contract, 
except as set forth in paragraph C below, and to pay the company for each 
ton of 2000 lb. avoirdupois of coal delivered and accepted in accordance with 
all of the terms of this contract at the following contract rate per ton of 
each respective contract grade, at which rates the company will deliver the 
following respective numbers of B.t.u. for one cent, the contract guarantee : 

Kind of Coal Contract Rate per Ton Contract Guarantee 

$ Equal to net B.t.u. for 1 cent 

<}• >( <( (I 

d» << a << 

Said B.t.u. for one cent being in each case determined as follows : 

Multiply the B.t.u. per lb. of dry coal by the per cent 
moisture, expressed in decimals, and subtract the product so 
found from the B.t.u, Then multiply the remainder by 2000 
and divide this product by the contract rate per ton plus one-half 
the ash percentage, both expressed as cents. 

C. It is provided that the consumer may purchase for con- 
sumption at said premises coal other than herein contracted for test purposes, 
it being understood that the total of such coal so purchased, shall not exceed 
5 per cent of the total consumption during the term of this contract. 

D. It is understood that the company may deliver coal hereunder con- 
taining as high as 3 per cent more ash and as high as 3 per cent more mois- 
ture and as low as 500 fewer B.t.u. per pound dry than specified above for 
contract grades. 

E. Should any coal delivered hereunder contain more than the per cent 
of ash or moisture or fewer than the number of B.t.u. per pound dry 
allowed under paragraph D hereof, the consumer may, at its option, either 
accept or reject the same. 

F. All coal accepted hereunder shall be paid for monthly at a price per 
ton determined by taking the average of the delivered values obtained from 
the analysis of all the samples taken during the month, said delivered value 
in each case being obtained as follows : 

Multiply the number of B.t.u. delivered per pound of dry 
coal by the per cent of moisture delivered, expressed in decimals, 
and subtract the product so found from the B.t.u. delivered per 
pound of dry coal. Then multiply the remainder by 2000 and 
divide this product by the contract guarantee. From the quotient, 
expressed as dollars and cents, subtract one-half of the ash per- 
centage delivered, expressed as cents. 
How such a rule works is illustrated in the diagram. Fig. 218, in 
which the standard is 9 per cent moisture, 8 per cent ash and 13,500 
.B.t.u. per pound of dry coal at $3 per ton. Coal of 500 B.t.u. and 3 per 
cent each of moisture and ash, either below or above the specification base, 
is the minimum acceptable and the maximum practicable, respectively, as 
shown in the diagram. On this basis the average premium or penalty is a 
little over 5 cents for each 100 B.t.u. above or below the standard. 

An Ohio street railway company has specifications drawn on a basis 
of a graded scale of premiums and penalties. The established standard for 
heat value ranges from 12,610 to 12,759 B.t.u. per pound of dry coal. The 
standard for ash is from to 15 per cent and for sulphur from to 3.5 per 
cent. The premiums on heat value are graded to a maximum of 21 cents 
per ton, above the basic price, for 13,960 B.t.u. and over. The penalties 




o 

c 

U 

6 
U 

u 



O 

'a 
B 

CO 

u 






o 

n 

.S 

X 
vo 

CO 

l-l 
O 



CO 



FUEL 



489 





^ 


N 












































\ 






































\ 


S 




X 


\s 
































3^0 






\ 






^ 


'fix 








■§ 


























V, 


X 










































\ 


^t 




^ 


N 


■o 




































\ 






^ 


N, 




















1 1 












■s 


N 






V 


















i , 
















"x 


k. 




X 


N 










^ 






















.§ 




\ 


^ 




X 


s. 


,^ 




























'g 






"N^ 


X 


^ 


^ 


^ 




























S; 








y^ 


^ 


s. 




V 


\ 
























^ 




^ 


y 








\ 






3.00 








Con 


fra 


zt P 


r'Ice 








^ 


^ 














V 


X 


















y 


^ 


































'> 


,y 




































^ 


0^^ 




































'\ 




































^ 


X 




































y 
















































































































































































































200 



300 400 liBOO 600 

B.+.u. per Pound Dry Coal 



Fig. 218. 



Comparison of Base Price and Price to be Paid for 
Coal Bought on Specifications. 



are also graded to as high as 50 cents per ton for heating powers of 10,660 
to 10,809 B.t.u. There is no premium for the minimum ash content, but 
there is a penalty for excess ash, amounting to 50 cents per ton when the 
ash is 29.1 per cent and higher. The penalty for sulphur above the standard 
is graded to 45 cents per ton when the content is 10 per cent or more. 

This contract provides that should the coal company or contractor fail at 
any time to supply the quality and quantity of coal specified, the consumer 
may purchase a supply in the open market, at prevailing rates, and collect 
from the contractor any difference in cost. The company reserves the 
right to cancel and relet the contract should the coal company fail to meet 
all the terms specified. 

The contract of a New York transit company gives an average premium 
and exacts an average penalty of about 2 cents for every 100 B.t.u. above or 
below the standard. Its standard is 14,201 to 14.250 B.t.u., 20 per cent 
or less volatile matter; 9 per cent or less ash, and VA per cent or less sulphur. 
For heat values above the standard the premium reaches 26 cents per ton for 
15,505 B.t.u. per pound of dry coal. For values below it the penalty is a 
maximum of 45 cents per ton at 12,000 B.t.u. or lower. The other penal- 
ties are highest at 18 cents a ton for 24 per cent or more of volatile matter ; 
23 cents for 13>4 per cent or more of ash, and 12 cents for a maximum of 
2^ per cent sulphur. 

The IJ. S. Government, a large user of coal for power and heating pur- 
poses, buys fuel under specifications that merge the heat value, ash, moisture 
and price, into a single unit of cost per 1,000.000 B.t.u. Provisions are made 
for penalties and premiums with respect to the contract standard. 



490 FUEL 



The intent of the specifications is to insure a coal deliven- similar 
within reasonable limits to the standard of the contract and not continually 
to make corrections in price for slight variations in heat value. A 2 per cent 
variation from the standard is allowed before the price is corrected, as it is 
recognized that the quality- of the coal cannot be controlled within narrow 
limits. Orders of 50 tons or less are sampled only at the discretion of 
the Government, because the collecting and preparing of a representative 
sample, and the cost of analysis, would considerably increase the cost. 

Under these specifications it is possible to utilize the output from a 
group of coal mines. Anthracite for power and heating purposes includes 
the pea and buckwheat sizes from the mines in the counties of Susquehanna, 
Lackawanna. Luzerne, Carbon. Schuylkill. Columbia. Sullivan. Northumber- 
land and Dauphin, in the state of Pennsylvania. Coal accepted as bitumi- 
nous includes the usual bituminous grades, as well as semi-bituminous, sub- 
bituminous, and lignite. 

All the coals are analyzed and tested by the Bureau of Mines, on the 
basis of its specifications. The main provisions for bituminous and anthra- 
cite coal are : 

Proposals. Sealed proposals, in duplicate, on blank forms supplied 

by the — , to furnish such quantities of coal as 

specified herein as may be required for use of the 

for the fiscal year ending — , will be received until 

2 o'clock p. m., _ , at the office of the , 

and then opened. 

Each bidder shall have the right to be present either in person or by 
attorney, when the bids are opened. 

Proposals, in duplicate, must be forwarded to the . 

postage prepaid. 

Proposals must be made in duplicate on the form provided, and must 
be signed by the individual, partnership, or corporation making the same. 
When made by a partnership, the name of each partner must be signed. If 
made by a corporation, proposals must be signed by the oflficer thereof 
authorized to bind it by contract, and be accompanied by a copy, under 
seal, of his authority to sign. 

The proposals must be accompanied by cash or by certified check drawn 

payable to the order of the , in the amount equal 

to 2 per cent of the estimated amount involved for the fuel for which bids 
are submitted, the minimum amount in any case to be $10. This requirement 
is solely to guarantee, if the award is made on the proposal, that within 10 
da^'s after notice is given that an award has been made, the bidder will 
enter into a contract in accordance with the terms of the proposal and execute 
a bond for the faithful performance thereof, with good and sufficient sure- 
ties as hereinafter required. In the event of the failure of the bidder to 
enter into contract or execute bond, the cash or check guarantee will be 
forfeited. 

Bond. Each contractor shall be required to give a bond, with two or 
more individual sureties or one corporate surety duly qualified under the 
act of Congress approved Aug. 13. 1894. in which the contractor and the 
sureties shall covenant and agree that, in case the said contractor shall fail 
to do or perform any or all of the covenants, stipulations, and agreements 
of said contract on the part of the said contractor to be performed as therein 
set forth, the said contractor and his sureties shall forfeit and pay to the 
L'nited States of America any and all damages sustained by the L'nited States 
b)^ reason of any failure of the contractor fully and faithfully to keep and 
perform the terms and conditions of his contract, to be recovered in an 
action at law in the name of the United States in any proper court of 



FUEL 491 

competent jurisdiction. Such sureties (except corporate sureties) shall justify 
their responsibility by affidavit showing that they severally own and possess 
property of the clear value in the aggregate of double the amount of the 
above-mentioned forfeiture over and above all debts and liabilities and all 
property by law exempt from execution. The affidavit shall be sworn to 
before a judge or a clerk of a court of record or a United States attorney, 
who must certify of his own personal knowledge that the sureties are suffi- 
cient to pay the full penalty of the bond. 

If the estimated amount involved in the contract does not exceed the 
sum of $200, then the bond may be waived with the consent of the depart- 
ment involved. 

Reservations. The right is reserved by the Government to reject 
any and all bids and to waive technical defects. Bidders are cautioned 
against guaranteeing higher standards of quality than can be maintained in 
delivered coal, as the Government reserves the right to reject any and all 
bids, if the Government has information regarding analyses and test results 
that indicate that higher standards have been offered than probably can be 
maintained. 

The right shall be reserved by the Government to purchase for the 
purpose of making boiler tests, other coal than that herein contracted for, pro- 
vided the amount so purchased shall not exceed 10 per cent of the estimated 
consumption during the period covered by this agreement. 

If it should appear to be to the best interests of the Government to do 
so, the right is reserved to award the contract for supplying coal at a price 
higher than that named in a lower bid, or in lower bids. 

If the bidder to whom the award is made shall fail to enter into a 
contract as herein provided, then the award may be annulled and the con- 
tract let to the next most desirable bidder without further advertisement, 
and such bidder shall be required to fulfill every stipulation expressed therein, 
as if he were the original party to whom the contract was awarded ; pro- 
vided, however, that such bidder is notified of said award within 60 days 
after the date on which the bids on this contract were opened. If such 
notice should not be given within said 60 days, then the acceptance of the 
award will be optional with the said bidder. 

No contract can be lawfully transferred or assigned. 

No proposal will be considered from any person, firm, or corporation 
in default of the performance of any contract or agreement made with the 
United States, or conclusively shown to have failed to perform satisfactorily 
such contract or agreement. 

Quantity. The estimated quantity of coal in tons 

of 2,000 lb. to be purchased is based upon the previous annual consumption, 
but the right will be reserved to order a greater or less quantity, subject to 
the actual requirements of the service. 

Delivery. The coal shall be delivered in such quantities at such times as 
the Government may direct. (Place of delivery to be stated.) 

All the available storage capacity of the Government coal bunkers shall 
be placed at the disposal of the contractor to facilitate delivery of coal 
under favorable conditions. When an order is issued for coal, the contractor 
upon commencing a delivery on that order shall continue the delivery with 
such rapidity as not to waste unduly the services of the Government 
inspector. 

After verbal or written notice shall have been given to deliver coal 
under this contract a second notice may be served in writing upon the 
contractor to make delivery of the coal so ordered within a reasonable 
time, to be determined by the Government official in charge, after receipt 
of said second notice. Should the contractor for any reason fail to comply 



492 



FUEL 




o 
DQ 

C 



73 

a 
a 

"5 

6 
o 
U 



> 

c 
Q 



o 

o 
CO 

O. 

c 
o 



FUEL 493 



with the second request, the Government shall be at liberty to buy coal inde- 
pendent of this contract, and for coal so purchased to charge against the con- 
tractor and his sureties any excess in price over the price which would have 
l)een paid to the contractor had the coal been delivered by him. 

The contractor shall be allowed to deliver coal during the usual hours 
of teaming — that is, between 8 a. m. and 5 p. m. 

Weighing. (To be stated, by whom and where the coal shall be 
weighed.) 

Sampling. The contractor shall have the privilege of having a repre- 
sentative present to witness the collection and preparation of the samples to 
be forwarded to the laboratory. 

The samples shall be collected and prepared in accordance with the 
method given in the appendix, attached hereto as a part of these specifica- 
tions and proposals. 

Analyses. The samples shall be immediately forwarded to the 
Bureau of Mines, Department of the Interior, Washington, D. C, and they 
shall be analyzed and tested in accordance with the method recommended 
by the American Chemical Society and by the use of a bomb calorimeter. 
Such analyses and tests shall be made at no cost to the contractor. The 
results shall be reported by the Bureau of Amines in not more than fifteen 
days after the receipt of the sample. If more than one sample is received 
from the same delivery, the fifteen days shall date from the receipt of the 
last sample taken. 

Description of Coal Desired. The coal must be a good coal 

(kind and size to be specified), and must 

be adapted for successful use in the particular furnace and boiler equipment. 

Bidders are required to specify the coal offered in terms of moisture in 
the coal "as received," and of ash, volatile matter, sulphur, and B.t.u. in 
"dry coal," such values to become the standards for the coal of the successful 
bidder. In addition, the bidders are required to give the trade name of 
the coal offered, and other designation ; this information shall be furnished 
in spaces provided hereinafter. 

Coal of the description and analysis specified is herein known as coal of 
the contract grade. Bidders are cautioned against specifying higher stand- 
ards than can be maintained, for to do so will result in deductions in price 
and may result in the rejection of the delivered coal or the cancellation of 
the contract. In this connection it should be recognized that the small 
"mine samples" usually indicate a coal of higher economic value than that 
actually delivered in carload lots, because of the care taken to separate 
extraneous matter from the coal in the "mine samples." 

Award. In determining the award of this contract consideration will 
be given to the quality of the coal (expressed in terms of moisture in coal 
"as received," of ash in "dry coal," and B.t.u. in "dry coal"), offered by 
the respective bidders and to the operating results obtained with the same 
and with similar coals on previous contracts or by test, as well as to the 
price per ton. 

Bids may be rejected from further consideration if they offer coals 
regarding which the Government has information that they possess unsatis- 
factory physical characteristics or volatile matter or sulphur or ash con- 
tents, or that they are unsatisfactory because of clinkering or excessive 
refuse, or because of having failed to meet the requirements of city smoke 
ordinances, or for other cause that would indicate that they are of a 
character or quality that the Government considers unsuited for the storage 
space or the furnace equipment of the particular contract. 

Methods of Comparing Bids. In order to compare bids as to the quality 
of the coal offered, all proposals shall be adjusted to a connnon basis. 



494 FUEL 

The method used shall be to merge the four variables — moisture, con- 
tent, ash content, heating value, and price bid per ton — into one figure, 
the cost of 1,000,000 B.t.u. The procedure under this method shall be as 
follows : 

(a) All bids shall be reduced to a common basis with respect to 
moisture, by dividing the price quoted in each bid by the difference between 
100 per cent and the percentage of moisture guaranteed in the bid. The 
adjusted bids shall be figured to the nearest tenth of a cent. 

(b) The bids shall be adjusted to the same ash percentage by selecting 
as the standard the proposal that offers coal containing the lowest percentage 
of ash. The difference in ash content between any given bid and this 
standard shall be divided by two and the price in such bid, adjusted in 
accordance with the above, multiplied by the quotient. The result shall be 
added to the above adjusted price. The adjusted bids shall be figured to 
the nearest tenth of a cent. 

(c) On the basis of the adjusted price, allowance shall then be made 
for the varying heat values by computing the cost of 1,000.000 B.t.u. for 
each coal oft'ered. This determination shall be made by multiph'ing the 
price per ton adjusted for ash and moisture content by 1,000,000, and dividing 
the result by the product of 2.000 multiplied by the number of B.t.u. guar- 
anteed. If the coal is purchased on the basis of 2,240 lb. to the ton, the 
factor of 2,240 should be used instead of 2.000. 

After the elimination of undesirable bids, the selection of the lowest 
bid of those remaining on the basis of the cost per 1,000,000 B.t.u. may be 
considered by the Government as a tentative award only, the Government 
reserving the right to have practical service test or tests made under the 
direction of the Bureau of Mines, the results to determine the final award 
of contract. The interested bidder or his authorized representative may 
be present at such test. 

Coal Subject to Rejection. It Is understood that coal containing 3 
per cent more moisture, or 4 per cent more ash, or 3 per cent more 
volatile matter, or 1 per cent more sulphur, or 4 per cent fewer B.t.u. than 
the specified guaranties as to the standards for the coal hereunder contracted 
for, or coal furnished from a mine or from mines other than herein speci- 
fied by the contractor, unless upon written permission of the Government, 
shall be considered subject to rejection, and the Government may, at its 
option, either accept or reject the same. Should the Government have con- 
sumed a part of such coal subject to rejection, such consumption shall not 
impair the Government's right to cause the contractor to remove the remain- 
der of the delivered coal subject to rejection. 

It is agreed that if the contractor shall furnish coal in three consecu- 
tive deliveries, or in case more than 20 per cent of the coal delivered to 
an}' date during the life of this contract shall contain 3 per cent more mois- 
ture, or 2 per cent more ash, or 3 per cent more volatile matter, or 1 per 
cent more sulphur, or 2 per cent fewer B.t.u. than the specified guaranties 
as to the standards for the coal hereunder contracted for, or if the coal is 
furnished from a mine or from mines other than herein specified, unless 
upon written permission of the Government, then this contract maj', at 
the option of the Government, be terminated, or the Government may, at its 
option, purchase coal in the open market until it may become satisfied that 
the contractor can furnish coal equal to the standards guaranteed, and the 
Government shall have the right to charge against the contractor any excess 
in price of coal so purchased over the corrected price that would have been 
paid to the contractor had the coal been delivered by him. 

Removal of Rejected Coal. The contractor shall be required to re- 
move, without cost to the Government, within 48 hours after notifica- 
tion, coal that has been rejected by the Government. Should the contractor 
not remove rejected coal within the said 48 hours, the Government shall then 



FUEL 495 



be at liberty to have the said coal removed from its premises and to dispose 
of such coal by sale, as the Government shall elect. The proceeds from such 
sale, less all costs incidental to its removal and to the sale, shall be paid over 
to the contractor. 

Determination of Price. The Government hereby agrees to pay 
the contractor within thirty days after the completion of an order or 
delivery for each ton of 2,000 lb. of coal delivered and accepted in accordance 
with all the terms of this contract, the price per ton determined by taking 
the analysis of the sample, or the average of the analyses of the samples if 
more than one sample is analyzed, collected from the coal delivered upon 
the basis of the price herein named, adjusted as follows for variations in 
heat value, ash content, and moisture content from the standards guaran- 
teed herein by the contractor. 

Heat Unit Adjustment. Considering the coal on a "dry coal" basis, 
no adjustment in price shall be made for variations of 2 per cent or 
less in the number of B.t.u. from the guaranteed standard. When the 
variation in heat units exceeds 2 per cent of the guaranteed standard, the 
adjusted price shall be proportioned and shall be obtained as follows : 
B.t.u. delivered coal ("dry-coal" basis) ^ ■• . , • 

B.t.u. ("dry-coal" basis) specified m contract 

The adjusted price shall be figured to the nearest tenth of a cent. 

As an example, for coal delivered on a contract guaranteeing 14,000 
B.t.u. on a "dry-coal" basis at a bid price of $3 per ton, showing by calo- 
rific test results varying between 13,720 and 14,280 B.t.u., there would be 
no price adjustment. If, however, by way of further example the delivered 
coal shows by calorific test 14,350 B.t.u. on a "dry-coal" basis, the price 
for this variation from the contract guaranty would be, by substitution in 
the formula : 

14,350 _ 

14000 ^ ?*^ — $0,075 

Ash Adjustment. No adjustment in price shall be made for varia- 
tions of 2 per cent or less below or above the guaranteed percentage of ash 
on the "dry-coal" basis. When the variation exceeds 2 per cent, the adjust- 
ment in price shall be determined as follows : 

The difference between the ash content by analysis and the ash content 
guaranteed shall be divided by two and the quotient shall be multiplied by 
the bid price, and the result shall be added to or deducted from the B.t.u. 
adjusted price or the bid price, if there is no B.t.u. adjustment, according 
to whether the ash content by analysis is below or above the percentage 
guaranteed. The adjustment for ash content shall be figured to the nearest 
tenth of a cent. 

As an example of the method of determining the adjustment in cents 
per ton for coal containing an ash content varying by more than 2 per cent 
from the standard, consider that coal for which the above-mentioned heat 
unit adjustment is to be made has been delivered on a contract guaranteeing 
10 per cent ash, and shows by analysis an ash content of 7.5 per cent. The 
adjustment in price would be determined as follows : 

The difference between 10 and 7.5 which is 2.5 would be divided by 2, 
and the quotient of 1.25 multiplied by $3, resulting in an adjustment of 3.7 
cents per ton, which in this case would be an addition. The price after 
adjustment for the variations in heating value and ash content would be 
$3,075 plus $0,037, or $3,112. 

Moisture Adjustment. The price shall be further adjusted for mois- 
ture content in excess of the amount guaranteed by the contractor, the 
deduction being determined by multiplying the price bid by the percent- 



496 FUEL 

age of moisture in excess of the amount guaranteed. The deduction shall 
be figured to the nearest tenth of a cent. 

As an example, consider that coal for which the above-mentioned heat 
unit and ash adjustments are to be made, and as having been delivered on a 
contract guaranteeing 3 per cent moisture, and that the coal shows by analysis 
4.5 per cent moisture; then the bid price would be multiplied by 1.5 (repre- 
senting excess moisture), giving 4.5 cents as the deduction per ton. The 
price to be paid per ton for the coal would then be $3,112, less $0,045, or $3,067. 

Partial Payment. If the coal on visual inspection by the Govern- 
ment inspector appears to be acceptable coal, the Government shall have the 
right, immediateh' on the completion of an order, to make payment on 90 
per cent of the amount of the bill, based on the tonnage delivered and 
the bid price per ton. The 10 per cent withheld is to cover an}' deduction 
on account of the delivery of coal that on analysis and test is subject to an 
adjustment in price. If the 10 per cent withheld should not be sufficient to 
cover the deduction, then the amount due the Government may be taken 
from any mone}- thereafter to become due to the contractor, or may be 
collected from the sureties. Because of the distance of the point of delivery 
from the laboratory, requiring several days for the transmittal of samples 
and the return of analytical report, because of loss of the original sample, 
necessitating the forwarding of the reserve sample, or for any other reason 
that would result in delayed pa3'ment, should such be withheld until receipt 
of analytical report, the Government may, as circumstances in its opinion 
warrant, exercise the foregoing right. 

Information to he Supplied. The following spaces should be filled 
in by the bidder for each bid, for if the information called for is not sup- 
plied, the proposal may be regarded as informal and rejected: 

The undersigned agrees to furnish to the 

the coal described below, in tons of 2.000 lb. each, and in quantity as may be 
required during the !iscal 3'ear ending, in accordance with the foregoing 
specifications; the coal to be delivered in such quantities and at such times as 
the Government may direct. 

(a) Kind and size of coal 

(b) Commercial name of coal 

(c) Xame of mine or mines 

(d) Location of mine or mines (town, county, and State) 

(e) Xame or other designation of coal bed or beds 

(f) Railroad on which mine or mines are located 

(g) Xame of operator of mine or mines 

(h) Percentage of moisture in coal "as received" 

(i) Percentage of ash in "dry coal" --. 

(j) Percentage of volatile matter in ''dry coal" 

(k) Percentage of sulphur in "dry coal'' 

(1) British thermal units per pound of "dry coal" 

(m) Additional description of coal deemed of importance by the bidder 



(n) Bid price per ton of 2,000 pounds. 



FUEL 497 



Specifications for Oil 

FUEL OILS are commonly specified according to their density. While this 
is accepted trade practice, it is not an accurate gage of the fuel. The heavy 
oils are of an asphalt base, viscous, sluggish, and of relatively low heating 
power. The light oils are fluid at ordinary temperatures, are volatile, rich in 
hydrocarbons and high in heating power. The heating power, however, de- 
pends mainly upon the hydrogen and carbon content, and when reduced to 
ultimate analysis these values are about the same for both heavy and light 
oils. The commercial value of fuel oil depends upon how easily it can 
be handled, or how completely it can be atomized by the burner equip- 
ment, and these features are controlled by the viscosity of the fuel. 

Viscosity can be defined as molecular friction or the resistance to inter- 
nal movement of a liquid. It is generally measured by the scale of a visco- 
meter, such as the Saybolt, Redwood or Engler, which indicates the time 
required for an amount of oil to flow through a standard orifice or short 
tube under fixed conditions of head and temperature. The result, some- 
times expressed in "degrees," is simply a time ratio. The type of viscometer 
should always be named in specifying viscosity, because the standards vary 
in different instruments. 

As the viscosity is materially lessened as the temperature Increases, the 
fuel oil in power-plant practice is heated to about 160 deg. before being 
fed to the burners. At this temperature, California oils have a vis- 
cosity between 3.5 and 8.5 deg. Engler. Many of the lighter oils are 
sufficiently mobile at ordinary temperatures and do not require pre-heating. 
In general, oil fuel is heated to within 50 deg. of the flash point for boiler 
operation with mechanical burners. 

The flash point of the fuel indicates the temperature at which inflammable 
gases or vapors are given off. For oil fuels, it ranges from 220 to 280 deg. 
For safety in handling this should not be below 150 deg. When stored in 
tanks and at ordinary temperatures, there is practically no danger as the 
oil does not form any appreciable amount of gas at temperatures below the 
flash point. The flash point is determined by heating the oil fuel, usually 
in a closed container, and testing with a spark or flame. The vapor or gas 
is driven off and flashes or ignites. The temperature at which ignition 
takes place is called the flash point. In the so-called open test an open 
vessel prolongs the flash point, the temperature being higher than with 
the closed instruments of Abel, Pensky or Marten, which are considered 
standard. 

By continuing the heating beyond the flash point until the flash becomes 
permanent and the fuel continues to burn a temperature known as the 
burning point is reached. As a free supply of air is required in this test, the 
open-cup method is used. For Kern River oil, the burning point can be taken 
as between 260 and 270 degrees. 

The properties of oil, as outlined, are of prime importance in the pur- 
chase of the fuel, and are therefore included in commercial specifications. 

Naval Specifications for Oil. The British Navy specifies a flash point 
not lower than 175 deg., closed-cup test. The water content must not exceed 
0.5 per cent ; sulphur not over 3. per cent ; and acidity expressed as oleic acid, 
a maximum of 0.05 per cent. 

The U. S. Navy requires a hydrocarbon oil of best quality, free from 
grit, acid and other foreign matter. A barrel of 42 gal,, each gallon of 231 
cu. in. at 60 deg., is the standard. For a variation of 10 deg. from the 
standard temperature, 0.4 per cent is added or deducted to correct the meas- 
ured quantity. The oil must not contain more than 1 per cent water and 
sediment. If over 1 per cent, the excess is either deducted from the volume 
or else the fuel is rejected. 



498 FUEL 

Viscosity at 100 deg. must not be higher than 200 Engler or 7000 seconds 
Saybolt. The flash point must not be below 150 deg. as the minimum 
by the Abel or Pensky-Marten closed-cup test, or 175 deg. by the Tagliabue 
open-cup method. For acceptance it should not be lower than the temper- 
ature at which the viscosity is 8 deg. Engler. /\s water is unity on the 
Engler scale, an oil having a viscosity of 8 deg. Engler at a temperature 
of 180 deg. will have a flash point of 180 deg. The equivalent of 8 deg. Engler 
is taken as 280 sec. Saybolt. 

Railroad Fuel Oil. The contract form of a large railroad system using oil 
as fuel, calls for the following : 

Fuel oil should have a density ranging between 13 and 29 deg. Baume 
at 60 deg. It should contain no sand or other foreign matter, such as 
sticks, waste and stone. The moisture content should be a minimum. Oil 
containing over 2 per cent water and other impurities will be rejected. 

Viscosity to be so low that the fuel oil will flow readily through a 4-in, 
pipe at 70 deg. temperature. 

Oil will not be accepted when the flash point is less than 110 deg. as 
tested by the Tagliabue open-cup method. The fuel is to be heated at the rate 
of 5 deg. per minute and the test flame applied at one-minute intervals after 
90 deg. has been reached. 

Goz'enijncnt Oil Fuel. For the purchase of oil fuel for the different 
departments of the U. S. Government, the Bureau of Mines has outlined 
the main features controlling the efficient utilization of fuel oil under 
steam boilers, as follows : 

Fuel oil should be either a natural homogeneous oil or a homogeneous 
residue from a natural oil ; if the latter, all constituents having a low flash 
point should have been removed by distillation ; it should not be composed 
of a light oil and a heavy residue mixed in such proportions as to give the 
density desired. 

It should not have been distilled at a temperature high enough to burn 
it, nor at a temperature so high that flecks of carbonaceous matter began 
to separate. 

It should not flash below 140 deg. in a closed Abel-Pensky or Fensky- 
Marten test. 

Its specific gravity should range from 0.85 to 0.96 at 59 deg. ; the oil 
should be rejected if its specific gravity is above 0.97 at that temperature. 

It should be mobile, free from solid or semi-solid bodies, and should 
flow readily, at ordinary atmospheric temperature and under a head of 
1 ft. of oil, through a 4-in. pipe 10 ft. in length. 

It should not congeal or become too sluggish to flow at 32 degrees. 

It should have a heating value of not less than 18,0(X) B.t.u. per pound; 
18.450 B.t.u. to be the standard. A bonus is to be paid or a penalty 
deducted according as the fuel oil delivered is above or below this standard. 

It should be rejected if it contains more than 2 per cent water or more 
than 1 per cent sulphur. 

It should not contain more than a trace of sand, clay, or dirt. 



499 



CHAPTER 14 



FEED W^ATER 

WATER, the most widely distributed liquid in nature, is the fluid gen- 
erally employed for converting heat energy into work by its expansion 
in the form of steam. 

Properties of Water 

CHEMICALLY pure water is a chemical combination of the two elements, 
hydrogen and oxygen, in the proportion of two parts hydrogen by 
volume to one part oxygen (H2O), or one part hydrogen by weight to eight 
parts of oxygen. Distilled water may be generally regarded as chemically 
pure. 

Water reaches its maximum density, 62.425 lb. per cu. ft. at 39.1 deg., 
and expands if this temperature is either raised or lowered. Fig. 219 shows 
its variation in weight and volume at temperatures from 20 to 250 deg. 
The values given are those at saturation pressure; that is, the pres- 



63 



62 



o 

i£ 

o 
x> 

D- 
«n 
T5 

c 

1 60 



32 



212 



59. 





1 




































1 






/ 




1 




































1 




t 






1 




































1 




/ 




'^ ' 


1 






"*- 






























1 


/ 








1 
1 












N 
























l/ 


/ 








1 














S 


s. 




















\ 










1 
















N 


s 


% 














/ 


1 










1 






















^ 










/ 




1 










1 




















1 


\ 








/ 


/ 




1 










1 
1 
























\ 






/ 






1 










1 


























\ 


/ 








1 
1 










1 


























/ 


\ 








1 










1 
























/ 






\ 






1 










1 




















^^> 


'/ 










\ 




1 










1 


















loV 














\, 


1 










1 

1 


















/ 
















V 


1.. 










1 
















Y 




















l^ 










1 












*^ 


y 






















1 


\ 
\ 








1 








^ 


X 


























1 




\ 




>•, 


1 


_ 




^ 






























1 






s 



20 50 100 150 200 

Temperature, Degrees Fahrenheit 



250 



,0170 
.0169 

.0168 



0167 

,0166 8 

0165 ^ 
ex 

.0164 S 

U- 

.0163 5 
.0162 



.0161 
,0160 



Fig. 219. Variation of Weight and Volume of Water with Temperature. 

sure at which liquid and vapor in contact at the same temperature will remain 
in equilibrium. For temperatures between 32 and 212 deg., the weights and 
volumes at atmospheric pressure are practically indistinguishable from those 
at saturation pressure, as water is almost incompressible. The dotted lines 
beyond these ranges represent the volume and weight of water in contact 
with steam at the pressures (above or below ordinary atmospheric) corre- 
sponding to the temperatiires given. 

The specific heat of water at 63 deg. is taken as unity, that is, it requires 
1 B.t.u. to raise a pound of water from 63 to 64 deg. The specific heat 
varies slightly at other temperatures, being 1.02 at 20 deg.; reaching its 



500 



FEED WATER 



minimum, 0.995, at 100 deg. ; and rising to 1.18 at 600 deg. The term, "mean 
specific heat" is applied to the difference in heat capacity per pound at two 
different temperatures, divided by the temperature difference. The mean 
specific heat of water from 32 to 175 deg. is 0.999, and for greater ranges it 
gradually rises, reaching 1.062 for the range from 32 to 600 deg. For many 
engineering purposes, the specific heat of water can be regarded as constant, 
and the heat liberated or absorbed taken as 1 B.t.u. per pound per degree 
of temperature change. 



25 



20 



s_ 

s: 
o. 

in 
O 

E 



15 



E 

> 



O 

in 

JZ 

o 

c 



u 



4- 
o 



10 




400 



350 



u 

300- 

t_ 

C5 

D 
O" 

250 fc 

D- 

w 
15 

C 
D 

200 a 



i_ 

D 
if) 

150 f 

Q. 

C5 

CD 



50 



-400 



-350 



300 ■§ 



i_ 

C5 

^ 

250^ 

i_ 

D- 

U) 
T5 

C 

200 p 



6) 

u 
D 
(/) 

to 

u 
D. 

O 



_5 

o 

100 < 



-150 



Fig. 220. 



100 150 200 250 300 350 
Boiling Point, Degrees Fahrenheit 

Variation of Boiling Point of Water with Pressure. 



Vapor rises from water at all temperatures, unless the vapor pressure 
in the space in contact with the water exceeds the saturation pressure. The 
boiling point for any particular pressure is the highest temperature which 



F E E D W A T E R 501 



can be reached with the water and vapor in contact with it at that pressure, 
any heat added to the water resulting only in the formation of additional 
vapor. In the generation of steam for practical purposes, the ebullition 
is of course much more pronounced than is the formation of vapor at low 
temperatures, but the phenomenon is similar in its nature. 

The boiling point rises and falls with the pressure, so that daily changes 
in the barometer have a slight effect on the boiling point; these must 
be allowed for in calibrating thermometers. The boiling point is reduced 
at points of high elevation and consequent low average barometric pressure. 

As long as heat is supplied to a boiler producing steam, the temperature 
remains at the boiling point corresponding to the momentary pressure, so 
that the temperature of boiler water in contact with saturated steam can be 
judged from the pressure. Fig. 220 indicates the boiling point for pressures 
up to 400 lb. gage. The divisions to the right indicate the corresponding 
pressures in absolute units, equal to 14.696 plus the gage pressure in pounds 
per square inch. Absolute pressures in pounds per square inch are converted 
into "standard atmospheres" by dividing by standard or normal atmospheric 
pressure (14.696 lb. per sq. in.), which is the pressure that will support a 
column of mercury 760 mm. (29.921 in.) in height. Roughly, 2 in. of mercury 
correspond to each pound of pressure. 

Pure water boils at 212 deg. under standard atmospheric pressure. For 
boiling points lower than 212 deg., the pressures are less than atmospheric. 
They are expressed as absolute pressures, in pounds per square inch or in 
head of mercury; or by the amount of "vacuum," that is, the difference 
between the absolute head of mercury and the standard atmospheric head of 
29.921 inches. For engineering purposes, the barometer is arranged so that 
the reading is subtracted from 30 instead of from 29.921, so that stand- 
ard atmospheric pressure when "referred to a 30-in. barometer" would be 
recorded as 0.08 in. of vacuum. 

Impurities in Water 

A LL known substances are more or less soluble in water, so that natural 
'^*' water supplies other than rain water are always contaminated, and 
contain in solution organic matter or traces of the solids with which they 
have come in contact. In a boiler, the solids remain behind when steam 
is produced, and the impurities are precipitated when their maximum con- 
centration is reached, that is, when the volume of water is sufficiently 
reduced to become saturated with the particular substance. These precipi- 
tates cause scale and accompanying troubles, the seriousness of which depends 
upon the nature and amount of the original impurities. 

The characteristics of a boiler feed water may be described by one or 
more of the following terms : temporary hardness, permanent hardness, 
alkalinity, causticity, acidity, and dissolved gases — the quantities of the im- 
purities being generally expressed in grains per U. S. gallon (231 cubic 
inches). 

Temporary hardness is the term applied to water containing the bicar- 
bonates of calcium, Ca(HC03)2, and magnesium, Mg(HC03)2, which are 
held in solution by an excess of carbon dioxide. Boiling at 212 degrees 
expells the carbon dioxide. In the one case, calcium carbonate, CaCO:!, pre- 
cipitates out directly. In the other, magnesium monocarbonate is formed. 
This is soluble and requires further treatment with calcium hydroxide. 
Ca(0H)2, to reduce to the precipitate Mg(0H)2. 

Sodium bicarbonate, NaHCOs, and sodium carbonate, NaaCOa, are found 
in the water in some localities. The former can be converted to the car- 
bonate by the use of calcium hydroxide, Ca(0H)3. 

Permanent hardness refers to those waters which contain sulphates, the 
most common of which is calcium sulphate, CaSO*. 




X 

o 

o 
o 



(U 



CO u 

CO <L) 

•^ CO 

J3 



>> 

C „ 

CO OJ 

a a 

o « 

o S 

^ CO 
O 

U 2 

(u o 
>PQ 

Q S 

dffi 



S 

CO 

CO 

o 



> 

G 

Q 



v?if^^"- --:^'s:Mi. 



F E E D W A T E R 503 



Solid calcium sulphate, CaS04, is known as plaster of Paris, or as 
gypsum when containing a larger amount of water of crystallization. It is 
highly soluble in water, 138 grains per gallon at 60 deg., and over 30 grains 
at 300 deg., but when concentrated, deposits a hard scale on the boiler tubes. 
It can be converted by the use of soda ash (sodium carbonate, NaaCOs), 
forming calcium carbonate, CaCOs, and sodium sulphate, Na2S04. The 
CaCOs can be precipitated before the water enters the boiler, but the Na2S04 
remains in solution, and does not interfere with boiler operation unless it 
becomes highly concentrated. 

Magnesium sulphate, MgSO*, is decidedly soluble, but tends to react 
with any calcium salts present, forming hard calcium sulphate scale. Water 
containing MgS04 can be treated by introducing calcium hydroxide, Ca(OH)j, 
forming insoluble magnesium hydroxide, Mg(OH)j, and calcium sulphate, 
CaSO^, which can be corrected by soda ash. 

Iron oxides, FeO, Fe203 and Fe304; aluminum oxide or alumina, AI2O3 ; 
and silicon oxide or silica, SizOa, are scale-forming substances sometimes 
found in solution. 

Alkalinity, a term often used confusedly with temporary hardness, refers 
more particularly to waters containing impurities which will neutralize acids. 

Causticity describes waters that contain hydrates which react to the 
phenolphthalein indicator. This test is important in connection with waters 
which may give caustic embrittlement trouble. 

Acidity, as the term implies, refers to waters containing free acid. In 
mining districts the water often contains sulphuric and sulphurous acids. 
Organic acids are found in swamp water and in water contaminated with 
sewage. Chlorides and acids present in boiler feed water are neutralized 
bj^ the reagents used to correct sulphates and carbonates. 

Calcium chloride, CaCl2, and magnesium chloride, MgCU, are found in 
boiler feed water. The latter is troublesome, as at boiler temperatures it 
tends to form hydrochloric acid, which causes corrosion. 

Solid matter such as mud and silt are often present in boiler water, par- 
ticularly if the feed water is obtained from rivers and streams. 

Dissolved gases, or air entrained or in solution, in boiler feed water is 
recognized as a source of corrosion. 

Water Analysis 

"T^ABLE 80 gives some representative analyses of water from various locali- 
-*■ ties. 

Methods of Water Analysis. Where it is proposed to prescribe a method 
of feed water treatment for a boiler plant, it is obvious that water analyses 
should be carried out in a laboratory equipped especially for the purpose. 
However, there are a number of simple tests which can be performed in the 
boiler room with a minimum outlay for apparatus, and which will indicate 
to the plant engineer the advisability of installing feed water treatment. 

Test for Hardness. A 100 cubic centimeter sample of the water for 
analysis, together with a standard soap solution, is shaken in a flask; the 
soap solution being added a little at a time until a permanent lather is formed. 
The number of cubic centimeters of the standard soap solution required to 
form the permanent foam will be equivalent to the hardness in parts per 
100,000, or in degrees "U. S." hardness depending upon the standard to 
which the soap solution is made up. One degree "U. S." hardness is equiva- 
lent to 1 grain of calcium carbonate per U. S. gallon (1 part in 58.349). 
Standard soap solutions may be obtained from chemical dealers. If this 
soap test is made on unboiled water, the total hardness will be determined, 
and if on boiled water, the permanent hardness will be obtained, the difference 
between the two being the temporary hardness. 



504 



FEED A\' A T E R 



Table 80. Water Analyses. 
("Boiler Waters" by W. W. Christie) 
Grains per U. S. Gallon of 231 Cubic Inches. 



Where From 









u 


-^ 








» »-j 


X 


•c s-S 


s ^ ^ 




■^^ ^. 


d 


IN 




E3 


=11 


V«)latile 
Organic 
Matter 



O 01 



Buffalo, X. v., Lake Erie 

Pittsburgh, Allegheny River.. . . 
Pittsburgh, Monongahela River 



5.66 
0.37 
1.06 



3.32 0.58 
3.781 0.58, 
5.12' 0.64 



0.37 
0.78' 



0.18 
1.50 
3.20 



9.74 

6.60 

10.80 



Pittsburgh, Pa., artesian well . . 23.45 
Milwaukee, Wisconsin River. . .| 6.23 
Galveston, Texas, 1 ' 13 . 68 



5. 71, 18.41 

4.67! 1-76 

13.52326.64 



1.04 
20.14 
Trace 



0.821 49.43 

6.50| 39.30 

Trace Z^i . 84 



Galveston, Texas, 2 I 21 . 79 

Columbus, Ohio 20. 76 

Washington, D. C, city supply.' 2.87 



29.15 

11.74 

3.27 



398.99 4.00 453.95 

7.021 0.58| 6.501 46.60 
Trace' 0.36' 2.10 8.60 



Baltimore, Md., city supply.. .. ! 2.77 0.65 
Sioux Citv, Iowa, city supplv . . 19 . 76j 1 . 24 
Los Angeles, Cal., 1 '. . . 10.12| 5.84 



Trace 0.10 3.80 
1.17| 1.031 4.40 
3.51 2.631 4.10 



7.30 
27.60 
26.20 



Los Angeles, Cal., 2. . . . 
Bay City, Mich., Bay. . 
Bay City, ]Mich., River. 



3.72 
8.47 
4.84 



12.59 

10.36 20.48 
33.66 126.78 



0.76 
1.15 
3.00 



6.00 
8.74 



23.07 
49.20 



10.92 179.20 



Cincinnati, Ohio, River 3 . 88| . 78 

Watertown, Conn 1.47| 4.51 

Fort Wayne, Ind 8.78 6.22 



1.79 

1 . 761 Trace 
3.511 1.59 



Trace 

1.78 

10.98 



6.73 

9.52 

31.08 



Wilmington, Del , 10 . 04 

Wichita, Kan 14.14 

Springfield, 111., 1 ' 12.99 



6.02 

25.91 

7.40 



4.291 8.48 

24.34 

1.971 2.19 



6.17f 35.00 
2.00: 66.39 
8.62' 33.17 



Springfield, 111., 2 5.47 4.31; 1.56| 4.28 

Hillsboro, 111 14.56; 2.97 2.391 1.63 

Pueblo, Colo 4.32' 16.15 1.20 1.97 



5.83| 21.45 

Trace! 21.55 

5.12 28.76 



Long Island City, L. I.. . . . 4.0 28.0 16.0 

Mississippi River above Missouri 

River 8.24 1.02 0.50 



1 





25 



39.0 
15.01 



Mississippi River below mouth 
of Missouri River 

Mississippi River at St. Louis 
Water Works 



10.641 7.41 1.36 1.22 
9.64' 6.94, 1.54 1.57 



15 
9 



86 36.49 
85 29.54 



Hudson River above Pough- 

keepsie, N. Y 1 . 06 

Croton River above Crotoni 

Dam, N. Y I 4.571 



0.16 



0.11 10.76 

! 

0.4o| 1.92 



771 12.70 
67^ 7.72 



Croton River water from service' I 

pipes in New York City ', 2.36 

Schuvlkill River above Phila- ! 

delphia, Pa 2.16| 0.29 



0.49 



1.36 

1.30 



3.72 
4.24 



Inasmuch as it is the custom to specify the hardness in terms of calcium 
carbonate per U. S. gallon, the following factors may be used to reduce the 
quantities of other salts present in a water to a calcium carbonate basis. 
Magnesium carbonate X L19 "I 

Magnesium sulphate X 0.833 Hardness as calcium 

X 1-05 >-= carbonate per 
X 0.735 I U. S. gallon 
X 0.901 



Magnesium chloride 
Calcium sulphate 
Calcium chloride 



FEED WATER 



505 



A water containing more than 20 grains of calcium carbonate, magnesium 
carbonate or magnesium chloride per U. S. gallon, or more than 5 grains of 
calcium or magnesium sulphate per U. S. gallon, is considered undesirable 
for boiler feed. 

Table 81 roughly classifies the desirability of hard waters for boiler use. 

Table 81. Classification of Boiler Feed Waters. 



CaCO. 

MgCO:, 

MgCl2 


CaS04 
MgS04 


Classification 


to 10 gr. 
10 to 15 gr. 
15 to 20 gr. 
20 to 30 gr. 
Over 30 gr. 


to 2.5 gr. 
2.5 to 4.0 gr. 

4 to 5.0 gr. 

5 to 7.5 gr. 
Over 7.5 gr. 


Very Good 
Good. 
Fair. 
Bad. 
Very Bad. 



Alkalinity Test. A 50 cubic centimeter sample of the water to be 
tested is titrated with a standard solution of sulphuric acid, using methyl 
orange as an indicator. The degree of alkalinity will be represented by the 
number of cubic centimeters of acid used to neutralize the solution, as will 
be indicated when the color of the solution just turns from pink to pale 
Aellow. The required standard sulphuric acid solution can be obtained from 
chemical dealers. 

Causticity Test. A 50 cubic centimeter sample of the water is titrated 
with a standard solution of sulphuric acid, using phenolphthalein as an indi- 
cator. The degree of causticity will be represented by the number of cubic 
centimeters of acid used to satisfy the reaction, as will be indicated when 
the solution turns from red to colorless. 

The alkalinity, hardness and causticity of a properly treated boiler water, 
as expressed in grains per U. S. gallon by analysis, should stand in the 
approximate relation of 6, 5 and 4. 

Concentration Test 

THE total concentration of soluble salts in a boiler fed with softened 
water can be estimated from the amount of sodium chloride or common 
salt (NaCl) in solution, which can be determined as follows: After blowing 
down the boiler, a sample is drawn from the water column, allowed to cool 
and settle, and 100 cc. of the clear liquid measured ofif. A drop of phenol- 
phthalein solution is added to the latter, turning it pink; then just sufficient 
N/20 sulphuric acid (about ^ per cent strong) from a burette to destroy 
the pink; and four drops potassium chromate indicator (containing 20 grains 
per 100 cc). Silver nitrate solution is then added slowly from another 
burette, while stirring the sample, until a permanent reddish precipitate is 
formed. If the silver nitrate solution is of a strength of 4.976 grains AgNOs 
per liter, each cubic centimeter of the solution consumed represents 1 grain 
of sodium chloride per gallon in the boiler water. 



Water Treatment 

\YyATER treatmefit may be roughly classified into three separate divisions, 
'^ viz : mechanical treatment, thermal treatment and chemical treatment. 

Mechanical Treatment. Raw water from rivers very often contains mud 
and silt in suspension, and if used directly in boilers will cause the deposi- 




c 
a 

Q 
u 



^- — 



O c 

— 3 



u 

.t: « 

^ G3 



o 

m 

'0 

O 

cu 



F E E D W A T E R 50/ 



tion of mud on the heating surfaces, resulting in lowered heat transmission, 
burned tubes and bagged plates. Such solid matter may be removed by- 
settling, filtering or by a combination of these two methods. Heavy mud 
and sand can be eliminated by allowing the water to stand in settling basins, 
but suspended matter which will not gravitate must be removed by filtration. 
Settling basins are generally constructed of concrete. They should be ar- 
ranged in duplicate so that while one basin is settling the other may be 
drawn upon as the supply. The size of such basins will depend upon the 
characteristics of the particular water as regards sedimentation, which may 
be roughly determined by experimental tests conducted on not less than 
barrel samples. Filter beds may be constructed of coke, excelsior, crushed 
stone or sand, and they should be arranged in duplicate to allow for clean- 
ing. 

Thermal Treatment. As stated above, the carbonates of lime and mag- 
nesia are precipitated by boiling, hence it is obvious that any type of feed 
water heater will act to a certain extent as a purifier or softener. A descrip- 
tion of the various types of heaters and of economizers is given in Chapter 
9 on AUXILIARIES. 

Chemical Treatment 

"T^HE chemical methods used for softening boiler feed water have been 
-*• practically unchanged for more than 50 years, except for special methods 
devised to obtain softened cold water. Hydrate of lime in the form of lime 
water, or of milk of lime, is still the most economic means for neutralizing 
acids, absorbing carbon dioxide, and converting bicarbonates to carbonates 
or hydrates. Likewise, soda ash is preferred for transforming sulphates, 
chlorides and nitrates to carbonates. While the chemical methods have not 
been changed, the engineering appliances for performing the softening process 
have undergone a radical evolution. The improvements have consisted prin- 
cipally in the proper use of heat for accelerating the chemical reaction, the 
more accurate feeding of chemical reagents, and the reduction in the labor 
required in handling chemicals and in removing precipitates. 

Two general types of lime-soda processes are used in power plants. In 
all essential respects, these two, the hot continuous and the cold continuous, 
processes, are similar. The treatment consists of adding to the raw water 
softening agents in carefully controlled amounts (which must agree with the 
composition of the water), mixing these thoroughly within the water, and 
permitting sufficient time to elapse for the separation of the "sludge" before 
the water is fed into the boiler. In the first process, the heat increases the 
rapidity of the chemical reactions, so that the storage space required is 
less than with the cold continuous process. The hot process expels the air 
from the water and so reduces corrosion. The cold process is used mainly 
when cold water is required for some special purpose, such as process work. 

Most softeners are of the continuous type. In intermittent softeners, 
two or more tanks are intermittently filled with raw water and chemicals. 
The treated water is then drawn off from one tank, while the other is filled 
and agitated by a revolving paddle so as to insure mixing and to stir up old 
sludge, which assists in settling out the new precipitate. 

The water softening apparatus usually includes some method of mixing 
the raw water with the chemical reagents ; the chemical reactions occur and 
the impurities are precipitated in a sedimentation tank. Sometimes the raw 
water is then passed through a filter tank. 

Chemical Feed. Chemicals must be fed to a softener accurately in pro- 
portion to the amount of water and to the impurities in the water. Other- 
wise the water will deposit scale, or will contain an excess of unused reagents. 
In some softeners the raw water flowing to the softener turns a water wheel 
or operates a tilting bucket. This in turn operates dippers in which the re- 



508 F E E D W A T E R 



agents are ladled out to be mixed with the raw water. In one design part 
of the water is separated from the main supply by oritices or weirs, and 
flows through chambers containing the reagents. In another type, the water 
displaces the reagent from the tank, at tlie same time diluting that w^hich 
remains in the tank. The raw water is sometimes passed through a hydraulic 
motor, which drives a small chemical pump. The feed can also be controlled 
by hand, an operator adjusting the chemical pump to deliver the required 
amount of solution each hour. Results are more satisfacton.', however with 
the automatic feed. 

Sedimentation Tanks usually have a conical base, into which the precipi- 
tates settle. The hot water and softening reagents are delivered at the top, 
and settle to the bottom, where the clarified water is withdrawn. In some 
designs (see Fig. 221) an open feed water heater is placed above the sedimen- 
tation tank. The heating chamber of the softener can be divided into two 
compartments, one for heating the raw water, and the other the pure water 
supply, the latter passing directly to the boiler feed pump. 

Filters. In some installations a separate filter is often dispensed with, 
the sedimentation tank removing the impurities. Under other conditions a 
low-pressure sand filter is placed between the sedimentation tank and the 
boiler feed pump or meter, the water flowing through bj' gravity. The water 
delivered should be crystal clear, containing no solids except those in solu- 
tion, and practically no mud-forming properties. This clarified water will 
leave no troublesome deposit in the feed lines, pumps or meters, and is 
especially suitable for boilers operated at high ratings. 

In the hot process water softener, Fig. 221, the raw water flows over 
heating trays, where it is heated bj* exhaust steam purified of oil to a tem- 
perature within a few degrees of the steam itself. The water falls from 
the trays into the sedimentation tank. Immediateh- after the water is heated 
to the boiling point or near it, the softening chemicals are added. In certain 
waters, they may be added above the heating trays. A precipitate is formed, 
which settles toward the bottom of the sedimentation tank, traveling much 
faster than the water. Due to the lower viscosity of hot water, the precipi- 
tation is much more rapid than in cold water. As a result the precipitate 
passes to the conical bottom, from which it is removed by opening the blow- 
off valve. 

A chemical proportioner is used to regulate tlie proportion of lime and 
soda ash to the raw water. A thin plate with a restricting orifice, is placed 
in the raw water line between the regulating valve and heater. A differential 
pressure is set up on the two sides of the plate, proportional to the square of 
the flow. This pressure is continually translated to an effective direct pres- 
sure on the chemical orifice. The chemical solutions and the raw water 
each pass through their respective orifices at exactly the same effective pres- 
sure, so that the chemical? are always accurate!}' proportioned to the raw 
water. 

The chemical treatment is controlled by drawing a sample of the treated 
water from time to time and titrating with standardized solutions, the whole 
operation requiring about ten minutes. The titration readings are obtained 
and then located upon a chart supplied with the softener, from which the 
correct chemical treatment is immediately read. Thus the operator sees at a 
glance what change, if any, is required in the amounts of the chemicals. 

Zeolite Process. This process gives a water of zero hardness. The 
softening agent is an artificial material (permutit) composed largely of sodium 
compounds, which are exchanged for the incrusting (scale-forming) material 
of the water. The hard water flows over the permutit which is packed in 
a cylinder, or is forced through and flows from it with all scale-forming 
material removed. The softener must be regenerated from time to time by 
allowing a solution of salt to flow over it, thus restoring its original com- 



FEED WATER 



509 




510 FEED WATER 



position and actlvit}'. If the water is of a high degree of temporary or 
carbonate hardness, the zeolite process introduces a large amount of sodium 
salt, and foaming may occur. With such waters the zeolite process is modified, 
an intermittent or continuous equipment being connected through* a filter 
to a zeolite softener. Only lime is used in the tank, the soda compound being 
secured from the zeolite. The filter is placed between the tank and the 
zeolite softener to avoid any sludge coating the permutit particles, and thus 
impairing its efficiency. 

Boiler Compounds. Boiler compounds for scale prevention are ex- 
tensively used in sm^all isolated plants where the expense of a water-soften- 
ing plant would not be warranted. While it is to be admitted that all 
chemical reactions necessarj^ to prepare a feed water should preferably take 
place outside of the boiler itself, there is no doubt but that a compound suit- 
able for particularly bad conditions and correctly used is to be preferred to 
no treatment at all. 

Results of Poor Water on Boiler Operation 

IDRIMIXG describes that phenomenon occurring in steam boiler operation, in 
■*- which water is delivered in belches with the steam. 

Foaming of boilers is the production of large quantities of bubbles in 
the steam space. 

If this water is carried out of the boiler, it erodes turbine blades, 
increases the steam consumption and causes waste of lubricating oil in 
reciprocating engines, while if the steam passes to a superheater, the water 
may carry solids to accumulate there as scale. 

Foaming and priming is encouraged by the presence of finely divided 
suspended matter, such as carbonate of lime, or of oil or soluble salts, such 
as sodium sulphate, either originally present or produced by the action of 
water-softening chemicals. At maximum capacity, water-tube boilers will 
stand a concentration of 200 to 300 grains of sodium sulphate per gallon; 
when foaming begins, the impurities can be removed by the use of the 
surface and bottom blow-offs. Even though some heat is lost, the removal 
of sediment and the stopping of foaming increases the efficiency. 

Foaming is also encouraged when oil is contained in the feed water 
introduced into boilers. The oil tends to collect on the tubes, to interfere 
with heat transmission, and to break down into corrosive acids. Oil carried 
in the exhaust steam from reciprocating engines or auxiliaries is removed 
by passing the steam through a separator rather than by skimming or 
filtering the condensate. The latter method is ineffective when the conden- 
sate contains oil in an emulsified or finely-divided state. 

Corrosion of boiler plates, tubes and rivets may be almost uniform in 
effect, in which case the action is difficult to detect, or it may be manifested 
by visible grooving and pitting. 

Corrosion of boiler metal is an electrolytic phenomenon by which a 
neutral iron atom, in contact with two positive hydrogen ions in the water, 
takes up their positive charges and becomes subject to oxidation. The 
hydrogen film formed tends to reduce the speed of the reaction almost to 
zero unless oxygen from the air or from acid-forming compounds is present 
in the water. The removal of carbon dioxide or other acids by chemical 
treatment, and the de-aeration of the water by pre-heating will prevent 
corrosion. 

Electrolysis or galvanic action with its resultant corrosion of the boiler 
metal, occurs frequently in marine practice, due principally to the presence of 
salt (NaCl) and air in the feed water. Zinc plates are therefore placed in 
the drum to act as the electro-negative element, thus hindering corrosion. 
See the description of the Heine Marine Boiler in Chapter 1. 



FEED WATER 



511 



Caustic Emhrittlcmcnt is a phenomenon which has lately received con- 
siderable study, but as yet its action is not definitely established. In certain 
localities in which boiler waters are of an alkaline character the development 
of cracks around seams and rivet holes below the water line have caused 
failures which can not be attributed to faulty materials or design. In- 
vestigation of the subject seems to disclose the fact that these failures are 
due \o an embrittlement of the boiler metal. This embrittlement is pre- 
sumably caused by the metal absorbing nascent hydrogen in such a way as 
to impair its physical properties. This effect has been decidedly pronounced 
in boilers using water containing a considerable amount of caustic soda, 
which has been present either due to over-treatment of the water, or as the 
result of the decomposition of the sodium bicarbonate NaHC03 occurring in 
the raw water. 

Scale Formation 

SOLUBLE carbonates and sulphates when concentrated in the boiler are 
precipitated as solids, which tend to accumulate and become baked into 
hard layers known as "scale," which has a high heat insulating value. As a 
result, fuel is wasted, and the metal becomes overheated. Expansion and con- 
traction strains follow and may greatly shorten the life of the tubes. _ Reports 
from boiler insurance companies show that the majority of boilers inspected 
are damaged from impure feed water by scale or by corrosion and pitting. 



Q_ 


o> 


1 


Cs! 




Q 


c^ 


~ 


■n: 


01 


o 


CS) 


cu 


1_ 




D 


r 


+- 


CSi 


o 


rsf 


L. 


^ 




C9 


E 


-Q 


Ci) 




1- 


f^) 




O 


1_ 


L. 


-+- 


t) 


n 


1- 


^ 




T5 

C 


O 


o 



1500 
[400 
1300 

1200 
IIOO 
1000 
900 
800 
700 
600 

50^ 
400 
300 
ZOO 
100 








































































/ 


/ 
































y 


/ 
































/ 


/ 
































/ 






























A^ 


/ 




















J- 


^ 










AO^ 


"^ 






















¥ 








v\< 


A/ 
























^A 


/ 






^> 




















^ 






c 


f 




y 


fA 


> 


r 








\o^ 


^. 




^ 








c 


?/ 






y 






^ 


C 












.■^i)' 


/ 




/ 




q 


c^ 


p^ 
















i 


f/ 


/ 


/ 












?h 


^f-e 




= 




- 


_ _ 





[^ 


/ 




^ 


" 




Cfe^ 








^ 




^ 


—" 























o 
o 
o 



— rg 



O O 



Heat Transmitte^d pe-p sq. ft. of Boiler Surface 
per Hour,B.TU. 

Fig. 2 22. Effect of Scale on Heat Transmission. 



Fig. 222, by E. RcuiVmgcr , shows the high temperature difference neces- 
sary in operating bolters with variation of heat transmission and of scale 
thickness. For the clean heating surface, the rate of transmission was 166 
B.t.u. per sq. ft. per hour per degree difference between the metal and the 
water; for the plate coated with Scale No. 2, which was 0.217 in. thick, of 
conductivitv 23.85, the rate was reduced to Q B.t.u. ; and for the plate 
coated with Scale No. 3, of the same thickness, but of conductivity 8.06, 
the transmission raJ;e was only 31 B.t.u. For a plate with a heavy grease 



512 



FEED ^^' A T E R 



coating the rate was 13.5 B.t.u. The necessary temperature differences 
can be read on the scale to the left, which shows that with scale the metal 
must be maintained at a temperature several hundred degrees above that of 
the water, when the boiler is driven at the rates now common. 

The heat losses, which may be as great as 10 per cent, the damage to 
the boilers themselves, the cost of repairs and cleaning ; all these emphasize 
the importance of preventing the formation of scale. Distilled water if 
used exclusively is prohibitive in cost. The onl}' practical method, when 
scale-forming matter is present in the water, is to form soluble salts or 
non-scale producing precipitates. Sodium carbonate (soda ash) can be used 
for transforming sulphates, chlorides and nitrates to carbonates, while 
calcium hydroxide (lime water or milk of lime) will correct acids and 
bicarbonates. 




Two 200 H. P. Heine Cross-Drum Marine Boilers on the Dredge-boat "Dixie". 
Board of Port Commissioners, New Orleans, La. 



513 



CHAPTER 15 



BOILER TESTING 

BOILER testing should not be lightly undertaken by anyone who has 
not had some training under an experienced testing engineer if reliable 
results are to be expected. The whole matter should be thoroughly 
understood both theoretically and practically. 

Accurate tests depend very largely upon the care and faithfulness of the 
observers. It is much easier to make mistakes than is realized by those 
who are not familiar with practical testing. 

Boiler tests are run to compare different boilers, stokers, etc. ; different 
kinds of fuel; different methods of operation, and so forth; but the object 
of the trial in every instance is to determine capacity, or efficiency in relation 
to capacity. To more definitely check the results, and to find the cause of 
unusually low or high efficiency by investigating the losses, the performance 
of the test and the analysis of the observations become more elaborate. 

The Rules for Conducting Evaporative Tests of Boilers, formulated by 
the American Society of Mechanical Engineers, 29 West 39th Street, New 
York, should be obtained and studied. All boiler tests should be made and re- 
ported in conformity with these rules, so that intelligent comparison with 
other boiler tests may be made. 

A new edition of the A. S, M. E. Code will be available about the time 
this book is published. If the following directions for conducting boiler 
tests conflict with the new Rules, the Rules must be followed in preference; 
but it is not expected that any serious differences will occur. In several 
instances where it was considered appropriate, parts of the A. S. M. E. Code 
of 1915 have been copied. 

To facilitate understanding the preparations for and making of boiler 
trials and computing the results, the subject will be treated in two parts. 
In the first part, the simpler tests will be considered where the capacit}^ only, 
or the efficiency and capacity, are wanted. In such instances, only the useful 
work done is measured, and the observations may be restricted to those 
necessary to attain this end. In the second part, the further observations and 
calculations necessary to prepare heat balances will be discussed. This 
work includes finding the amount and cause of the losses as well as the 
amount of useful work done. 

Personnel 

HTHE person conducting the test should have sufficient assistance to enable 
-*- him to oversee at all times everything connected with the test. He 
should satisfy himself from time to time that the weighing scales, instru- 
ments, etc., are giving correct indications and that all readings are being 
correctly and punctually recorded. He should continually be on the alert 
for any change in conditions, such as an unusual demand for steam, stoppage 
of stokers, fans, feed pumps, and so forth. His assistants should be chosen 
for their enthusiasm no less than for their ability ; and it may prove wiser 
to abandon and repeat the test rather than continue with an assistant who 
shows contempt for, or lack of interest in, the proceedings. 




o 









t- ^ 



:S 



T. 



TESTING 515 



Condition of Boiler 

'T~'HE condition of the boiler and furnace should first be ascertained, and 
-^ described in the report of the test. If it is desired to demonstrate the 
value of improved operating conditions, then a test should be run without 
any change whatever, followed by another before which defective brickwork, 
baffles, etc., should be repaired, soot and scale removed and the boiler 
put in generally clean and first-class working condition. If the expected 
capacity or efficiency is not realized, the heat balance will probably show 
the cause ; and if the necessary observations for calculating a heat balance 
have not been made, then another test must be run for this purpose. Changes 
can then be made in whatever direction the losses in the heat balance point, 
and other tests run until the results expected are realized. Sometimes 
several tests are run to enable an efficiency curve to be drawn at different 
loads or to enable comparison to be made of operating under different 
working conditions. 

Duration 

'T'HE duration of the test must be sufficient to insure accuracy, and this 
^ is governed by the closeness with which the amount of fuel and water 
involved at start and stop can be ascertained. With oil, gas, etc., there is no 
store of fuel in the furnace, and four or five hours is generally sufficient. 
With coal, the amount of fuel in the furnace must be judged at start and 
stop; and as this is often little better than guesswork, a much longer period 
is necessary because the error in this judgment may be a noticeable per- 
centage of the total fuel burned. 

With mechanical stokers carrying a steady load, 10 hours may be suf- 
ficient, but if there is much variation in load this should be greatly increased. 
With hand firing, the duration should not be less than 8 hours for 
anthracite or 10 hours for bituminous coal. The trial should be long enough 
for at least 250 pounds of coal to be burned on each square foot of grate 
area. If an accurate efficiency test is desired, it should be continued for 24 
hours ; but for capacity only, 3 or 4 hours is sufficient. 

Simple Test Data 

TF the capacity only is wanted, the coal need not be weighed or analyzed; 
-^ but such tests are unusual since they give so little information. There- 
fore, only those tests will be discussed in which both capacity and efficiency 
are to be ascertained. 

Observations are necessary to obtain the following quantities: 

Weight of Feed Water 
Weight of Coal 
Heat Value of Coal 
Temperature of Feed Water 
Pressure of Steam 
Quality of Steam 

Particular accuracy is essential in determining the first three items. If 
any of these are incorrect, the test is useless. 

Weighing Feed Water 

I 'HE usual plan for weighing feed water is to have one or more tanks 

■'■ on scales at a high level, discharging by gravity to a single tank below. 

The lower tank should be larger than either of the others, and have no pipe 

connections except the suction line to the feed pump. The level of the 

water in the lower tank should l)e noted at the connncnccmcnt of the test 



516 TESTING 



and be brought back to this level at the end. The upper tanks may have 
overflows, but care must be taken that the overflow water cannot fall into 
the lower tank. The upper tanks must be large enough so that there is 
ample time for operating the filling and dumping valves, weighing the water 
and recording it. A simple rule will prevent mistakes — record immediately 
the time of dumping each tank: and if there are more than one tank, number 
them and record the time of dumping in separate columns. 

Water Meters are not considered sufficiently accurate or reliable for 
boiler testing; but in some instances it is almost impossible to avoid using 
them. They should be carefully calibrated before and after the test by 
weighing water metered into suitable tanks. When calibrating meters, 
care must be taken that all readings are from the same part of the cycle of 
motions operating the counter. As water meters measure volume, the 
temperature of the water during calibration must be taken, and the weight 
of water at that temperature used in the calculations. Water meters of the 
Venturi t>-pe, or weirs, are reliable ; but should be calibrated. Automatic 
water-weighers are installed in many large plants, and their readings may 
be used after calibration and examination as to reliability. 

Water Gage. A scale should be mounted close to the boiler gage glass so 
that the height of the water can be easib' read. Note should be made of the 
position of the scale and then it can be replaced accurately if the glass 
breaks during the trial. The position of the scale relative to the boiler must 
be definitely determined, so that the volume of water in the boiler cor- 
responding to any distance on the scale can be computed if necessary, as 
explained below. 

Water gages should not be blown down for at least one hour before 
starting and stopping, as this changes the water level in the glass, because 
the tem.perature and consequently the density- of the water in the gage and 
connecting pipe, is changed. 

The feed should be so managed that the water will be at the same level 
in the boiler at the end of the test as it was at the start. If this is not done, 
the difference in level must be allowed for b\' calculating the volume of 
water in the boiler between the two levels. The weight of water, calculated 
at the temperature in the boiler, must then be added or deducted as required. 
The correction for difference in level must always be made in this manner. 
Pumping in more water or blowing down are not permissible. 

Leakage. Care must be taken that all valves and fittings are tight. Blow- 
off pipes should be blanked off, or disconnected so that anj^ leakage can 
be s,Q.tn and measured. Where the feed pipe connects with other boilers, it 
ma}^ not be necessary to blank off these branches if they are provided with 
two valves with a drain cock or plug between, which may be kept open dur- 
ing the test to insure that no water is passing through leak>- valves. Un- 
avoidable leakage from pump stuffing boxes and so forth, must be weighed 
and deducted. 

Boiler leakage may be ascertained by closing all valves, maintaining 
pressure by means of a very slow fire, and noting the fall of water in the 
gage glass. Readings of this description should be taken even,- ten minutes 
and continued until they show a constant rate. 

Leakage from tubes in the feed water heater must be looked for. and 
any such leakage either measured or cured. 

Where drainage from heating s3'stems is automatically returned to the 
boiler, arrangements must be made to disconnect the system and discharge 
the condensate elsewhere during the test. 

The fundamental condition to keep in mind is that no water shall enter 
the boiler during the test except that w^hich is being weighed ; and that all 
the water which is weighed enters the boiler and leaves by way of the steam 
space only. 



TESTING 517 



Weighing Coal 

COAL should be weighed only about as fast as required, but the supply 
must always be ample. In this way the amount on the firing floor can 
easily be estimated at any time, such as hourly. The same simple rule recom- 
mended for feed is desirable here — record immediately the time of dumping 
each wiieelbarrow load. 

Never trust to marks or tallies for weighing coal or (cod water. 

IVeighing Scales for coal and water should be examined carefully to 
see that they swing freely, and should be tested to see that they balance 
at zero and with standard weights of aljout the amount at which they will 
be used. Platform scales arc generally most convenient for weighing feed 
water tanks and wheelbarrows of coal and ash. , 

Heat Value of Coal 

X-J EAT value of coal is fully treated in Chapter 13 on FUEL, where 
■*■ ■*■ methods of working down samples and of analysis are described, and 
representative analyses of fuels are given, 

A small sample should be taken from each wheelbarrow of coal be- 
fore weighing. The amount taken should be about 1 per cent with 
small anthracite and 2 per cent with bituminous coal. The bulk sample thus 
obtained should be worked down to about 10 lbs. as described in Chapter 13. 
Half of this is to be sent to the laboratory in an airtight fruit jar or similar 
airtight package, and the remainder kept for reference or to replace loss. 

The moisture in the coal is an important item and is difficult to get with 
accuracy. 

The moisture in the sample as received at the laboratory can be deter- 
mined with fair accuracy. But since coal readily absorl)s or gives ofif moisture 
according to the humidity of the atmosphere, different analysts will often 
obtain different results from the same sample. 

Unless the bulk sample while being collected during the test and while 
being worked down to a laboratory sample is kept in a cool place, it will not 
be representative as to moisture. If the sample is collected and worked 
down in a warm and drafty place, it may possibly lose as much as 2 per 
cent of water or even more. 

Therefore, it is often preferable to determine the moisture during the 
test, and for this purpose a small pair of scales is required, sensitive to about 
^4 oz. when weighing about 20 pounds. A sample of about 20 lbs. (separate 
from the main bulk sample) is carefully selected to be representative as to 
moisture, shortly after commencement of the test ; and after weighing, it is 
spread out on a sheet iron tray and exposed to a temperature of about 250° 
F. for several hours. Care must be taken to protect the sample from strong 
drafts which might blow away some of the dry dust; and it is advisable to 
cover the tray with a perforated sheet iron cover, leaving a space of an inch 
or two between it and the coal. The tray may l)c placed on a flue or 1)reech- 
ing ; but it must not be allowed to get too hot or some of the volatile matter 
will be distilled off, thus giving an erroneous result. It may be necessary 
to support the tray on bricks or the like to prevent the sample getting too 
hot. For this determination, the coal should be crushed down so that the 
largest pieces are not over Yx inch. The sample is carefully weighed before 
and after drying for about four hours and then weighed every hour after- 
wards until two consecutive weighings agree. The loss in weight divided 
1)y the weight before drying, multiplied by 100 is the percentage of moisture 
referred to coal "as fired." 

Feed Water Temperature 

pEED water temperature must be taken with a thermometer having the 
"*■ scale graduated on the glass stem. There sliould be several spare ther- 
mometers so that breakage will not cause stoppage of the test. 



518 T E S T I X G 



The thermometer is placed in a thermometer-well screwed in the feed 
pipe. The well should be deep enough to reach to the center of the pipe, 
or at least well into the flowing water. It should not be in a pocket where 
the flow is sluggish. The well may be filled with mercun.- or oil. Response 
to changes of temperature is not as quick with oil as with mercurj- ; but unless 
there are unusually rapid changes of temperature, oil is quite good enough. 

Recording thermometers are desirable when there is much fluctuation, 
but they should be checked against the regular indicating thermometer 
readings. 

Thermometers and thermometer-wells are described in Chapter 11 on 
HEAT, to which reference should be made as to care and methods of use. 

Steam Pressure 

TD RES SURE gages should be tested with a dead-weight tester with both 
^ rising and falling pressure, and the case should be tapped gently to see 
that the mechanism is free. Allowance must be made for head of water 
in the connecting pipe if there is any. 

Recording gages are useful for boiler testing, but their accuracy must 
be established. The pen or other recording device must be quite free to 
move with slight pressure fluctuations. The clock error — fast or slow — in 
relation to the clock or watch used for the test, must be ascertained and 
recorded. 

Ample s^'phons must be provided to prevent steam reaching the gages. 

Care of gaees and methods of use are described in Chapter 16 on 
OPERATION. ^ 

Quality of Steam 

IF the steam is not superheated, it m.ust be tested for the amount of moisture 
or entrained water present. For this purpose the throttling calorimeter is 
used when the moisture does not exceed 4 per cent, and the separating calo- 
rimeter for wetter steam. 

The Throttling Calorimeter was invented by Prof. C. H. Peabody, and has 
long been used with complete satisfaction. It is dependent upon the 
adiabatic expansion of steam through a nozzle. The heat converted into 
work as velocity* of the steam, is returned to the steam as sensible heat when 
the steam loses its velocity in the expansion chamber. As the total heat in 
the steam is the same after expansion to atmospheric pressure as it was 
at boiler pressure, it is obvious that some or all of the moisture present in 
the high pressure steam will be evaporated. If too much moisture is pres- 
ent, the resulting mixture will have a temperature of 212° F., while with drv* 
steam the temperature will be much higher, showing considerable superheat. 
From tlie amount of superheat of the expanded steam, the amount of moisture 
present in the steam before expansion can be readily calculated. 

Taking dr\- saturated steam of 150 lbs. gage pressure, the total heat per 
pound is 1196.1 B.t.u. The total heat per pound at atmospheric pressure is 
1151.7, and the difference or 44.4 B.t.u. is used in superheating the steam at 
atmospheric pressure. 

If the steam contains 2 per cent of moisture the total heat is, for the 
steam : 

0.9S X 1196.1 =-- 1172.18 
for the water : 

0.02 X 337.8 =z 6.77 



1178.95 B.t.u. 
The total heat in one pound of dry steam at atmospheric pressure and 
212° F. is 1151.7, and the difference. 

1178.95 — 1151.7 = 2725 B.t.u.. 
is available to superheat the steam after the moisture has been evaporated. 



TESTING 



519 



As the specific heat of steam is 0.46, the amount of superheat will be : 

27 25 
±i^ _ ego -p 

0.46 ~^^ • 

The temperature of the expanded steam will be shown by the thermom- 
eter as : 

212 + 59 = 271° F. 

If a regular or standard instrument is not available for making the 
test, one may be made up of pipe-fittings as illustrated in Fig. 223. 




Fig. 223. Throttling Calorimeter. 



520 




CO 

a 



03 ;i 
I- o 

w C O 

CO U( M 

5 <u C 



X 



CO 

O 
o 

CO 

u 

a 

CO 



O 1^ CO 
O Xi 

c 

CO 



(4-1 "-^ 

Oil 
. CO 

PhPQ 






(U 

:i > 



gffiO 
o 

s 

o 



(U 



Bui 
o 



o 

(U 



TESTING 521 

A piece of 4-in. pipe, 10 to 12 in. long, and screwed caps on each end 
make up the body of the calorimeter. Openings in the end are provided as 
shown — steam inlet at A usually >4-in. pipe, thermometer and gage con- 
nections at T, exhaust outlet at N of at least 1-in. pipe. Care must be 
taken to offset the pipes A and N. The whole calorimeter is heavily lagged 
to prevent radiation. The nipple A, through which the steam enters the 
calorimeter, is made of composition, cut with pipe thread and provided with 
an orifice for reducing the pressure and gaging the flow of steam. It is 
shown in detail at (b). The orifice may be made Ve* inch. 

Steam passes from the main through the orifice in A, in which it expands 
and enters the chamber K at atmospheric pressure. If the calorimeter is 
properly lagged so that no heat is lost by radiation, the heat content of one 
pound of steam at the lower pressure in the calorimeter will be the same 
as that at the boiler pressure. 

Kent's formula for reducing the observations of the throttling calo- 
rimeter is : 

M= 100 X H ^ nSl.7- 0.46 (/s- 212) ^^3^ 

where : 

M = Percentage of moisture in the steam 

H = Total heat of the high pressure steam, P^ 

ts= Temperature of the steam in the expansion chamber of the 
calorimeter 

L = Latent heat of the high pressure steam. Pi 

With low pressure steam, the outlet N of the calorimeter may be con- 
nected to the condenser. In that case the latent heat 1151.7 and the specific 
heat 0.46 in formula (63) are replaced by those due to the lower pressure 
in the expansion chamber K. 

The Mollier diagram given on page 416 is particularly applicable to the 
solution of this problem. Its use is illustrated below : 

Example 1. Boiler pressure, 100 lb. abs. ; calorimeter pressure, 20 lb. 
abs. ; calorimeter temperature, 250 deg. Find the percentage of wetness 
in the steam. 

Locating on the diagram the intersection of the 20-lb. line, and that for 
the temperature 250 deg., we find the heat content to be 1173 B.t.u. Follow- 
ing this B.t.u. line until it intersects the 100 lb. pressure line, we read the 
quality as 0.98. The priming will be (1 — 0.98) 100 = 2 per cent. 

The range of use of the calorimeter depends upon the heat available to 
superheat the steam. This in turn depends upon the boiler pressure and the 
drop in pressure. To get sufficient accuracy, not less than 10 deg. super- 
heat in the calorimeter is necessary. 

The following is taken from the "Description of Steam Calorimeters" 
in the A. S. M. E. 1915 Code. 

"The percentage of moisture is determined by observing the number of 
degrees of cooling that the thermometer in the low-pressure steam shows 
below the 'normal' reading for dry steam, and dividing that number by 
the 'constant' number of degrees representing 1 per cent of moisture. 

"To determine the 'normal' reading of the low-pressure thermometer 
corresponding to dry steam, the instrument should be attached to a horizon- 
tal steam pipe in such a way that the sampling nozzle projects upwards to 
near the top of the pipe, there being no perforations and the steam entering 
through the open top of the nozzle. The test should be made when the steam 
in the pipe is in a quiescent state, and when the steam pressure is maintained 
constantly at the poi;it observed on the main trial. If the steam pressure falls 
during the time when the observations are being made, the test should be con- 
tinued long enough to obtain the effect of an equivalent rise of pressure. 



522 



TESTING 



To find the 'constant' for 1 per cent of moisture divide the latent 
heat of the steam supplied to the calorimeter at the observed pressure or 
temperature by the specific heat of superheated steam at atmospheric pres- 
sure (0.46) and divide the quotient by 100. 

"Frnallj- ascertain the percentage of moisture by dividing the number 
of degrees of cooling by the constant, as above noted. 

"To determine the quantity of steam used by the calorimeter it is usually 
sufficient to calculate the quantity from the area of the orifice and the absolute 
pressure, using Xapier's formula for the number of lb. which passes through 
per second; that is, absolute pressure in lb. per sq. in. divided by 70 and 
multiplied by the area of orifice in sq. in. To determine the quantity by 
actual test, a steam hose may be attached to the outlet of the adorimeter, 
and carried to a barrel of water on platform scales. The amount of steam 
condensed in a certain time is determined, and thereby the quantity dis- 
charged per hour." 

Separating Calorimeter. When the percentage of moisture is too large 
for the throttling calorimeter, the separating calorimeter, Fig. 224, is used. 
In this the moisture is mechanically separated, just as it is in the ordinary 
power-plant separator. Steam enters as indicated, passes down into the 
perforated basin from which dry steam escapes through small openings 
near the top, while the moisture is deposited in the bottom of the calorimeter. 
The dn^- steam passes through the jacket surrounding the water, from which 




Gradoased 
Scale 

Gaxige- 



Steam Jacket 



Water 



Discharge 

Oriice 



Fig. 224. Carpenter Separating Calorimeter. 



TESTING 523 



it is discharged through an orifice. This orifice can be used to measure 
the dry steam, or the discharge can be led to a condenser and the condensed 
steam weighed. The quantity of water separated in the reservoir can be 
determined by reading the special scale provided on the gage glass. The 
weight of water collected divided by the sum of the weights of this water 
and of the dry steam for the same period of time, gives a result which is the 
percentage of wetness. In practice the results obtained with the separating 
calorimeter are only approximately correct, because of the difficulty of draw- 
ing a representative sample from the pipe line. 

The calorimeter connection with the steam main, from which the sample 
of steam to be tested is taken, should be made according to A. S. M. E. 
recommendations. The ^-in. pipe should extend across the main to within 
>2-in. of the opposite side, the end being plugged. Around the circumference 
of this sample pipe should be drilled not less than twenty ]^-in. holes, 
spaced irregularly. The nearest hole should be at least ^-in. from the side 
of the main. 

Superheated Steam. Use a gas filled thermometer with enlarged 
bore at the upper end. The thermometer well should contain mercury or 
soft solder, and the immersed portion of the well should be fluted to cause 
quicker response to fluctuations of temperature. 

Where extreme accuracy is essential, make the stem correction as 
described on p, 373. 

Steam Tables 

'T'HE report of the test should state which steam tables the calculations 
-'- were based on. Goodenough's tables are given on page 424 and are 
used throughout this book. If Marks and Davis's or Peabody's tables are 
used, care must be taken to adopt their values as constants in the formulas 
where they occur, such as in finding the factor of evaporation. 

Starting and Stopping 

SPECIAL consideration of the methods to be used in starting and stopping 
the test is necessary. These must be well thought out beforehand, and 
be suitable for the particular conditions to be encountered. Sufficient error 
to render the test useless is easily introduced, unless the proper observations 
are made quickly and simultaneously and immediately recorded. 

With hand fired boilers, in order that the fire may be as nearly as pos- 
sible in the same condition at start and at stop, the fire must be burned low 
and cleaned both before the beginning and before the end of the test, so 
that a clean fire is left on the grate in each instance. Thin fires are more 
easily judged than thick ones. Bituminous coal fires should be 2 to 4 in. 
thick at start and stop, and small anthracite fires may be 1 to 2 inches. 
Colored spectacles should be used in examining fires, particularly so with 
forced draft and soft coal, for little is to be seen, much less judged with any 
accuracy, without them. 

To start the test, note quickly the condition of the fire, the water level in 
the gage glass, the water level in the lower or suction tank of the feed 
water tanks, and the time. Record these observations with the time as the 
start of the test. Record the first steam pressure reading and the first feed 
water temperature reading immediately afterwards. 

To end the test, watch the fire when and after being cleaned, and as 
soon as it is in the same condition as at the start, note the water level in 
the gage glass, the water level in the lower feed water tank (preferably 
stopping the feed pump) and the time, and record these as the end of the 
test. 




o 

CO 



O--- 



^ 


i£ 


u 





clc 


JJ" 


D 


u 


*. 


0' 


T3 
eg 


J2 


O 

u 






^ 


(S 


-,1 


X 


•o 




V 


^M 


a 


CO 


a 


4J 


3 


C 


cr 


o 


CO 


9i 


u 




u 


"o 


"T; 


c 







m 


s 


"o 


o 


u 


^ 


C3 


■«-• 


•o 




& 


Cm 

o 




09 

a 


o 


o 


r^ 






Xfl 


'C 




X 


!2 






"o 


'S 

c: 




u 


c 


3 


o 


n 


'^ 




OS 












OS 




•»-> 




00 




C 





o 



TESTING 525 



If there is any difference in the gage glass level at start and stop, 
allowance is to be made later by calculation. If the water level is low in 
the lower feed water tank, weigh the amount necessary to make up the de- 
ficiency and add it to the total water fed ; and if the water level is high, 
bale out and weigh the excess and deduct it from the total. 

When a water meter is used, the procedure at both start and stop is to 
note the condition of the fire, the water level in the gage glass, the reading 
of the meter, and the time. Record these observations with the time as the 
starting and stopping times respectively. 

Weigh back any excess coal left on the firing floor and deduct it from 
the total. 

In a plant containing several boilers where it is not practicable to clean 
them simultaneously, the fires should be cleaned one after the other as 
rapidly as may be, and each one after cleaning charged with enough coal 
to maintain a thin fire in good working condition. After the last fire is 
cleaned and in working condition, burn all the fires low (say 4 to 6 in.), 
note quickly the thickness of each, also the water levels, steam pressure, and 
time, which last is taken as the starting time. Likewise when the time 
arrives for closing the test, the fires should be quickly cleaned one by one, 
and when this work is completed they should all be burned low the same as 
at the start, and the various final observations made as noted. 

In the case of a large boiler having several furnace doors requiring the 
fire to be cleaned in sections one after the other, the above directions per- 
taining to starting and stopping in a plant of several boilers may be followed. 

Mechanical Stokers. To obtain the desired equality of condition of the 
fire when a mechanical stoker other than a chain grate is used, the procedure 
should be modified where practicable as follows : 

Regulate the coal feed so as to burn the fire to the low condition re- 
quired for cleaning. Shut off the coal-feeding mechanism and fill the 
hoppers level full. Clean the ash or dump plate, note quickly the depth and 
condition of the coal on the grate, the water level, the steam pressure, and 
the tim.e, and record the latter as the starting time. Then start the coal- 
feeding mechanism, clean the ashpit, and proceed with the regular work of 
the test. 

When the time arrives for the close of the test, shut off the coal-feeding 
mechanism, fill the hoppers and burn the fire to the same low point as at the 
beginning. When this condition is reached, note the water level, the steam 
pressure, and the time, and record the latter as the stopping time. Finally 
clean the ash plate and haul the ashes. 

In the case of chain grate stokers, the desired operating conditions should 
be maintained for half an hour before starting a test and for a like period 
before its close, the height of stoker gate or throat plate and the speed of 
the grate being the same during both of these periods. 

Report of Simple Test 

Observations should be made punctually and immediately recorded. When 
it is essential that a number of instruments be read simultaneously, there 
should be an observer at each one. A signal should be given, such as by a 
bell or whistle, when the readings are to be taken. 

The frequency of taking the readings of steam pressure and feed water 
temperature depends upon the extent and rapidity of the fluctuations. Usually, 
half hourly observations are sufficient ; but if there is considerable variation, 
readings should be taken every 15 minutes. 

Records. The observations should be recorded on separate sheets so that 
different observers are not hampered by having to write in the same book. 
The plan of the test must be arranged beforehand and the duties of each 



526 TESTING 

observer clearly defined. In important and complicated tests, one or more 
preliminary runs as rehearsals are very desirable. 

Make a note of every incident connected with the test together with the 
time of its occurrence, however unimportant or unnecessary it may appear 
at the time. 

The record sheets should either be printed or made up by hand before the 
test, and the original sheets should be kept, no matter how dirty they may 
be. Each record sheet should be dated and signed by the observer. As soon 
as possible after completing the test or even during its progress, the whole 
of the observations and remarks should be written up in a log book having 
pages not less than letter paper size — 11 in. by 8^4 inch. 

It is desirable that the records show the coal and water consumption 
each hour. This is easily done by allowing for the coal on the firing floor and 
for the height of the water in the gage glass at the end of each hour. But 
this is only incidental and the orderly procedure of weighing full tanks of 
water and of the regular quantity of coal must not be disturbed. 

Chart. Where there are fluctuations of load, steam pressure and so forth, 
it is advisable to plot a chart of the test. This may well be done while 
the test is in progress. Unlooked for conditions are shown at a glance. Fig. 
225 is a chart reproduced from the A. S. M. E. 1915 Code. 

The form of report shown in Table 82 is suitable for the simpler kind of 
test which has been described. Items may be added to record other 
observations if desired, such as draft in uptake and at other points, weight 
of water actually evaporated per hour, smoke, etc. 

Sketches, photographs and descriptions should be attached, giving any 
particular information such as condition of boiler and furnace, arrangement 
of baffles and so forth. 

Table 82. Evaporative Test. 



Description of Boiler Rated H. P 

Located at 

Date of Test Duration Conducted by 

Coal, Kind size cost per lb., $... 

Grate, Type area draft 

Heating surface, boiler superheater economizer. 



(1 
(2 
(3 
(4 
(5 
(6 
(7 

(8 
(9 
(10 
(11 
(12 

(13 
(14 



Steam pressure, lb. per sq. in 

Percentage of moisture in steam or superheat, °F. 

Factor of correction for quality of steam 

Feed water temperature, °F 

Factor of evaporation 

Equivalent evaporation per hour, from and at 212° F., lb 

Equivalent evaporation per hour, from and at 212° F. 

per sq. It. of heating surface, lb 

Percentage of rated capacity developed 

Percentage of moisture in coal 

Dry coal per hour, lb 

Dry coal per sq. ft. of grate surface per hour, lb 

Equivalent evaporation from and at 212° F. per lb. 

of dry coal, lb 

Heating value per lb. of dry coal, B.t.u 

Efficiency, per cent 



TESTING 

ItJoo JO oit?os 



527 



^§1 



oa *® 3 £5 2 °° 









— 








— 




■~~ 


















■n 








_ 
















K 










/ 


/ 












1 


^ 




















_ 
















c 


V 




~ 


^ 


^ 
















V 
















h 


If 


















::§< 
















— o. 








\ 


















l\- 
















~- 


^ 


^ 






















-^ 


i 














T 


f 


















S 


L 






. 




--■ 










\ 
















r 


















— 




"^ 




S 




1 — 















\ 


y 












T^ 


1 


















'-v 




s 












\f 






_\ 














/ 
















l- 


^ 









\ 




















\ 


V 










Y 




> 




















\ 


S^ 




















\ 












\ 


















i 












"t 


^ 


^ 


^ 
















^ 






''n\ 


C-8 j' 


pai 


iduitiK 












7 


L_ 






^ 


X 


















v 




E 


bqc 


nj m\ 


ijtjjfl 


Ijo 


ait 


'OS 
















Z\ 








f 




\ 


















N 


s. 








.. y. 


■rj- 


C3 














< 










\ 




^ 


\ 


















^ 








1 






















> 








I 


^- 




\ 


\ 


















^ 




i 


\ \ 






































\\ 
















\ 






V ^ 


















c3' 


< 


^ 


>- 
















' 














N 


1 




\ / 


b 




























^ 




\ 


\ 
















\, 




\^ 


■^ 




















1\ 








-- 


^ 

^ 








K 


^ 














N 


s 


1 




7 
















rt 




^^ 




















\ 
















\ 






5 
















c2 


X 






















^ 


\ 














\ 




<^. 


v^ 
























■y 


a 












\ 














r-\ 


<S 




/ 




















^ 








f 
















\ 












?K 




<i-i 


?^ 




















^ 






c 


1 
















S 












\ 


C 




















< 












' 


















\ 












\ 


Ql 


\ 


















'V, 










k 


h 
















-> 


. 










\ 




S 


1, 


















^A 










N 


\ 














%\ 










Y 






i 














c 


\ 












^ 


\ 
















-^ 


k 








\ 
























> 






F 
























N 


y 






\\ 






\ 
















< 








W 


























\ 






\ 


















.co_ 
m 

-I 












"^ 


■<^ 


^ 






















\ 




~T 






/ 


y 












(aSnx 


o 


nB 


ks 


JO 


9{t 


3S 


/ 


p 


















V 


V 








y 












o 


o 

CD 




in 


- 


o 




o 

CO 




A 


Y 






















\ 


) 




i 














>:^ 


























\ 






\ 


) 


















\ 




< 


\ 




























^ 


i 




) 


i 


















/ 


5 






N 


\, 




























\ 




j^ 


\ 
















/ 








/ 


^ 




























fk 




^ 


4 














c 


\ 








i 




























Oc 


J ^ 






^ 
















\ 








^ 




























S 


( 


\ 






\ 














\ 














^ 


■V 




















H 


\ 


\ 




/ 


\ 














^ 


" 
















•^ 


















3 


1 




N 


/ 


\ 














f 








/ 




























t:< 


/ 




f 1 


\ 














J 










'^ 






























Y~~ 




1 






\ 








s' 










■d 


as 


t^ 


533 


Al 


s 


|T30 


s 














den; 


>X 9"L 


I JPO 


nop 


/ 





\ 


\ 








^ 








. Ill 


o 




o 




^S 




o 




o 
o 














G 


o o 
o m 


1° 




/ 




\ 


-\ 


\ 








!- 






o 






/ 


























O 






< 


t— 






\ 


V 








S 












\ 






























" 




L 






^> 













V 


v^ 










k 
































k 


■»«,^ 






\ 


V 










> 












^ 


I 






























— ^"C 


^ 






\ 


s 
















^ 






^'^ 
























i 


o- 


' 
























^ 












*-> 


J 


































— 1 








__ 








__ 




^ 








^^ 


__ 


__ 































H 



^-4 



8 S 



8 



§ 8 



§* 8 



O O 



H 



o 

pq 



O 
bD 

d 



o 

J3 



O 



(to 



a9;c^ JO ai^og 



528 TESTING 



Calculation of Simple Test 

THE heading of the report should be filled in first. Xo explanation of 
this part is necessary, except to mention that the grate area is the 
horizontal area between furnace walls, so that the grate area is the same 
whether the grate is horizontal or sloping. In the following discussion, the 
numbers at the commencement of paragraohs are those of the items in 
Table 82. 

(1) This is the average of the observations. 

(2) ^lethods of finding the percentage of moisture in saturated steam 
have been discussed. With superheated steam, the temperature of saturated 
steam due to the pressure is found from the Steam Tables in Chapter 12 
on STEAM, and deducted from the temperature of the superheated steam, 
giving the number of degrees of superheat. 

(3) When the percentage of moisture is less than 2, it is suiticient 
merely to deduct the percentage from the weight of water fed, in which 
case the factor of correction for quality is : 

per cent moisture ,,, 

^-- wo '"> 

When the percentage is greater than 2, or if extreme accuracy is required, 
the factor of correction is : 

1-.U|=^' C65) 

in which M is the proportion of moisture, H the total heat of 1 lb. of 
saturated steam, g^ the heat in w^ater at the temperature of saturated steam, 
and q the heat in water at the feed temperature. 

When the steam is superheated, there is no factor of correction. 

(4) This is the average of the observations. If there is an economizer 
and the test is of the boiler and economizer together, then this ^tem is 
the temperature of the feed water entering the economizer. If the test is of 
the boiler only, this item is the temperature of the feed water entering the 
boiler, whether there is an economizer or not. 

(5) The factor of evaporation may be described as the amount of heat 
transferred to each pound of feed water passed through the boiler, divided 
by the heat necessary to evaporate a pound of water from and at 212°. 
Therefore : 

^=w' (^> 

where : 

F ^ Factor of evaporation 

H = Total heat of steam at boiler pressure or at pressure and tem- 
perature of superheated steam 
q = Total heat in water at feed temperature. 

Xo allowance is to be made for moisture in the steam, as this is taken 
care of in item 6. 

(6) The total weight of feed water is first corrected for differences 
in level of boiler water gage and in feed suction tank if necessary. If 
there is no superheater, this total weight is multiplied by item 3 to find the 
total water actually evaporated. This is multiplied by item 5 to find the 
total equivalent evaporation from and at 212^ F., and divided by the duration 
of the test in hours. 

(7) This is item 6 divided bv the actual water heating surface. 

(8) Item 6 divided by 34.5 gives the B.H.P. developed. The B.H.P. 
developed, divided by the rated H.P. of the boiler gives the percentage of 
the rated H.P. developed. 



TESTING 



529 



(9) This does not require further explanation. 

(10) The total coal weighed out is first corrected for differences in 
quantity in furnace at start and stop if necessary, and for any coal re- 
maining unused at end of test. The total weight of moisture as found by 
item 9 is deducted, leaving the total weight of dry coal. Dividing this by 
the duration of the test in hours gives the dry coal per hour. 

(11) This is item 10 divided by the grate area. 

(12) This is item 6 divided by item 10. 

(13) This is entered from the laboratory report. 

(14) This is item 12 multiplied by 971.7 and by 100, and divided by 
item 13. 

Complete Test Data 

A COMPLETE evaporative test includes several other observations in ad- 
■^^ dition to those already described. These observations are directed 
mainly to finding the parasitic losses by means of a heat balance. To begin 
with, an ultimate analysis of the coal will be required, and this will be 
stated as in item 25 of Table 86. 

Temperature of Exit Gases may be taken with a gas filled thermometer. 
To get the average in a large flue, specially long thermometers are made to 
reach to the center or at least well into the gas current. An oil pot, or 
large thermometer-well may be arranged to hang into the flue, and the 
thermometer will then have to be lifted out of the oil each time it is read. 




Fig. 226. Portable Indicating Instrument of 
Wm. H. Bristol Electric Pyrometer. 

Electric pyrometers of the thermo-couple type are the handiest instru- 
ments for the purpose. The portable instrument shown in Fig. 226 is most 
convenient, for it may be connected to several "hot ends." 

Various thermometers and pyrometers arc described in Chapter 11 on 
HEAT. 




CI 

09 

V 

C 



TESTING 



531 



The temperature of the air entering the ashpit, item 16 of Table 86, 
may be taken as that of the boiler room in natural draft plants. With forced 
draft, the temperature should be taken near the fan inlet. Inexperienced 
observers should be zvarned against the danger of accident unless the fan 
inlet is screened. If air heaters are installed, the temperature should be taken 
both entering the heater and entering the ashpit, and so reported. 

Particular care must be taken that the thermometer is not exposed to 
radiation from nearby hot surfaces. 

Flue Gas Analysis. The average composition should be represented in 
the samples collected. For use in computing heat balances, the sample should 
be taken so as to include air leakage into the setting, and the sampling 
tube should be placed in the uptake. Even in good commercial settings, the 
CO2 may drop as much as 3 or 4 per cent between the combustion chamber 
and the stack. This inleakage may not be excessive, but nevertheless the 
conditions should be known. The efficiency of firing operations can be 
studied by analyzing '"grab" samples taken from the furnace or from among 
the tubes, and plotting the results as shown on page 575. 

Perforated sampling tubes are sometimes used, but a plain, open-end 
pipe, drawing from the center of the flue, is generally favored. A radial 
"spider" is also recommended by the Bureau of Mines. Fig. 227 shows a 
sampling tube inserted in a Heine boiler. The tube should be placed at 
least 3 ft. below the damper and 1 ft. above the steam drum, through a 



Gas Sampling Pipe,, 



Plan of 
Uptake 




W^ 



Collector 



Fig. 227. Method of Inserting Sampling Tube. 



532 



T E S T : X c 



hole drilled in the brick wall and closed with asbestos packing. By con- 
necting an ejector to the ;:;e a 5: ?-ll stream of gas is constantly drawn ont 
with the steam or water, and are: ref er.tstive sample can be drawn at any time 
fro:.- :. e current moving tc in :/e ejector. A continuous or average 
sair.ne r^; resenting one to six hcurs iteration can be secured by the 
arra: ne: -e::: shown in Fig. 228w The :.:-er 2-gal. bottle, initial^ full of 



' ''e.-'—arUbfer 



Piressure 
Gauge 

Gas 




Fig. 2 28. Arrangement for obtaining Continuous or Average 

Sample of Flue Gas. 

water, is slowly emptied, drawing in the due gas. Such a sample produces 
an average upon the basis of time, rather than load, and is reasonably repre- 
sentative if the difference between the two water levels is 2 ft. or more, 
so as to maintain the effective head nearly uniform. If the sample is to 
stand over the water for more than two hours, or if it is subject to much 
variation in COs content, it should be collected over a saturated brine solution 
(one-fourth salt by weight) to minimize absorption by the liquid- All joints 
in the pipe connections should be tight and coated with asphaltum painL 
The Hne can be cleaned more easily if crosses having removable plugs are 
used instead of elbows, but the liability of leakage is increased. 

A water-cooled or quartz tube is desirable for the part of the sampler 
extending into the gas current, although a H to }^-rn. metal tube is satis- 
factory. For securing "grab" samples for combustion control, a ^ in. bore 
copper tube is preferable. It has less capacity for the same nominal size, 
and two or three rapid fillings of the burette suffice to clear it of air. 
It can be easily inserted through cleaning holes, so that samples can be taken 
from different points in the boiler. 

Gas Analysis Apparatus. For determining the composition of nue gases 
in ordinary- boiler work one of the simplest and most convenient instru- 
ments is the Orsat apparatus. This instrument can easily be used by the 
person conducting a test, or b\- some assistant whom he directs. 

Orsat Apparatus. The principal constituents of flue gas {CO^ O, and 
(Z0^ can be measured in the Orsat apparatus by passing a sample of the gas 
successively into three solutions, each having a high absorptive capacity for 
one of the constituent gases. 

The apparatus. Fig. 229. consists of a .reii :'^"?' bure::e. leveling bottle, 
three absorption pipettes and the connecti: :-. 71 r :rr::r 5 nlled with water 
by raising the leveling bottle. The flue gas :s ilien ad::-:::ed to the header, 



TESTING 



;33 



Pinch 
Cocks - 

Absorpiion 
Pipettes 

Rubber 
dags--- 




-^S7 ^27 ^S7- 

Levelinq 
Bottle 




Measuring 
Burette 

-Water 
Jaclxef 



Fig. 229. Orsat Apparatus for Analyzing Flue Gas. 

drawn into the burette, and rejected to the atmosphere. This is repeated 
several times until the water is saturated with CO2 and the system is hlled 
with gas. A 100 cc. sample is then taken into the burette by lowering 
the bottle until the surface of the water in the burette reaches the lowest 
graduation when it is at the same level as the water in the bottle, thus 
subjecting the sample to atmospheric pressure. Next comes the actual 
measuring. 

The gas supply is shut off, and the sample forced into the right-hand 
pipette, where the CO2 is absorbed by a solution of KOH, caustic potash. 
The sample is passed back and forth several times until its volume ceases to 
decrease, when the solution is drawn to its original level in the upper neck 
of the pipette and isolated again. The residual gas is then measured under 
atmospheric pressure, that is, with the water in the bottle and in the burette 
at the same level, and the loss in volume represents the percentage of CO2 
in the original sample. 

The connection is now opened into the second pipette, which contains 
an alkaline solution of pyrogallic acid. The oxygen in the remainder of 
the sample is absorbed and the percentage determined in the same manner 
as was that of the CO2. 

The third pipette contains an ammoniacal solution of cuprous chlo- 
ride, CU2CI2, which absorbs the CO, and the loss in volume in this third opera- 
tion gives the percentage of CO. The cuprous chloride absorbs both CO 
and oxygen, and would thus give an erroneous indication if all free oxygen 
was not first removed. The oxygen is determined primarily in order to 
ascertain the CO content. The analysis for O2 and CO is not ordinarily 
made unless the presence of CO is suspected, as when the CO2 percentage 
is high and the supply of air may be deficient. 

To prevent sudden temperature changes while the sample is being exam- 
ined, the measuring burette is encased in a water jacket. The front legs 
of the pipettes are filled with small glass tubing, to afford large contact 
surface between the solutions and the gas, while the rear legs of the O2 
and CO pipettes are closed to prevent contact of the solution with the air. 



534 




v: 



V 



'J 



r. 



n 



c 

3 
O 

U 

c 



u 



€ii;ii^^^ 



TESTING 



535 



This is not necessary with the KOH solution used for the CO2 
measurements. 

Orsat connections consist either of rubber tubings closed by pinch cocks, 
or of glass tubing with ground-glass cocks. The latter system is considered 
more reliable and operates satisfactorily when the cocks are clean and well 
lubricated. 

If momentary samples are obtained, the analyses should be made as 
frequently as possible, say every 15 to 30 minutes, depending on the skill of 
the operator, noting the furnace and firing conditions at the time the sample 
is drawn. If the sample drawn is a continuous one, the intervals may be made 
longer. 

For determining the hydrogen and other unburned combustible matter 
in the flue gases, and for general gas analysis, the Hempel apparatus, or 
some modification thereof, is required. Work of this kind should be entrusted 
to a person who is familiar with all phases of the subject. 

The Hempel Apparatus works on the same principle as the simple form 
of Orsat apparatus described, so far as the latter is applicable, except 
that the absorption may be hastened by shaking the pipettes bodily, bringing 
the chemical into most intimate contact with the gas. It is less portable and 
in some particulars it requires more careful manipulation than the Orsat, 
while for general analysis it is not adapted unless used in a well equipped 
chemical laboratory. The absorption pipettes are made in sets which are 
shaped in the form of glol)es, and a number of independent sets are required 
for the treatment of the different constituent gases. A simple pipette of the 
Hempel type is shown in Fig. 230. 




Hempel Pipette. 



The method of carrying on an analysis with the Hempel apparatus 
is as follows : 

A sample of gas measuring 100 cc. is drawn into the burette, and then 
transferred to the first pipette, wliich contains potassium hydrate dissolved in 
twice its weight of water. This solution absorbs carbon dioxide (CO2). 
The gas is then passed into the second pipette, containing saturated bromine 
water, which absorbs the heavy hydrocarbons (C2H4) ; then into the third 
pipette, containing a solution of pyrogallic acid and potassium hydrate in the 



536 TESTING 

proportion of 5 grams of acid to 100 cc. of h\-drate, which absorbs ox\-gen 
(O) ; then into the fourth pipette, containing ammoniacal cuprous chloride, 
which absorbs carbon monoxide (CO), and finally into the fifth pipette, 
which is of large size and provided with exploding wires and galvanic 
batter}-, for the determination of marsh gas (CH4) and hydrogen (H). A 
measured quantity of oxygen gas is added to this pipette and the contents 
exploded by an electric spark from the batten.-, resulting in a mixture of 
carbon dioxide, nitrogen and free oxygen. The quantity.- of carbon dioxide is 
determined by passing the gas into the pipette containing potassium hydrate, 
and the quantity- of oxygen b}- subsequent!}- passing it into the pipette con- 
taining potassium pyrogallate, finally determining the quantity of marsh gas 
and hydrogen from the known reactions which occur during this process, 
and the composition of the resulting gases. 

For each of these processes the pipettes are shaken to hasten the absorp- 
tion, and the quantity absorbed is determined by returning the gas into the 
measuring burette and observing the successive differences. 

The ashes and refuse withdrawn from the furnace and ashpit during the 
progress of the test and at its close should be weighed, so far as possible, 
in a drj^ state. If wet, the amount of moisture should be ascertained and 
allowed for, a sample being taken and dried for this purpose. This sample 
may ser^-e also for analysis for the determination of unburned carbon and 
for fusing tests. 

When the ashes and refuse are to be reported, the ashpit and combustion 
chamber must be cleaned at the beginning and end of the test, and the 
amount found at the end of the test weighed. 

The dust and ash from the combustion chamber, tubes and flues, should 
be weighed separately. With hea^-^- forced draft there maj- be a considerable 
amount. In some instances endeavor is made to determine the amount 
carried up the stack. But it is practically impossible to ascertain these 
quantities with any precision. 

The temperatures in the furnace and combustion chambers may be taken 
by means of electrical or optical pyrometers. These instruments are 
described in Chapter 11 on HEAT. 

Draff gages should be connected between each boiler and its hand- 
damper, and as near the damper as practicable. In the case of a plant con- 
taining a number of boilers, a gage should also be connected to the main 
flue between the regulating damper and the boilers. It is desirable also to 
have gages connected to different points of the gas passage through the 
boiler ; to the furnace or furnaces, and in the case of forced draft, to the 
ashpits and blower ducts. If there is an economizer, a gage should be con- 
nected to the flue at each end of it. 

The same draft gage may be used for all tlie points mentioned, provided 
suitable pipes are run from the gage to each, arranged so as to be readily 
connected to either point at will. 

Draft gages are discussed in Chapter 16 on OPERATIOX. 

The height of the barometer should be obser^-ed during important tests 
and the average given in item 15. It is common to add 14.7 lb. to the 
gage pressure to find the absolute pressure : but the actual atmospheric pres- 
sure as read from the barometer should be added instead if extrem.e 
accuracy is desired. 

The humidity of the atmosphere should be observed for particularly 
accurate work. The usual wet and dry bulb thermometer, preferably of the 
sling type, is suitable for this purpose. Table S3 gives the relative humidit}^ 
from the wet and dry bulb thermometers. Table 84 gives the weight of 
moisture present and Table 85 gives the weight of saturated air. The 
relative humidity- is entered as item 16. 



TESTING 



537 



Table 83. Relative Humidity, in per cent (Total Saturation = 100%). 

Barometer 29.92 in. 



Dry 
Thermometer 

op 


Difference between Dry and Wet Thermometers, Deg. Fahr. 


1 


2 3 


4 


5 


6 


7 


8 


9 





66.8 
78.1 
84.9 


34.0 
56.6 
70.0 


1.5 
35.3 

55.2 














10 


14.3 
41.0 












20 


26.9 


12.9 
















30 
40 
50 


89.1 
91.6 
93.5 


78.3 
83.4 
87.0 


67.5 
75.3 
80.6 


56.8 
67.5 

74.3 


46.5 
59.9 
68.0 


36.4 
52.4 
61.9 


26.3 
45.0 
55.8 


16.5 
37.7 
50.0 


6.8 
30.5 
44.3 


60 
70 
80 


94.5 
95.3 
95.8 


89.0 
90.6 
91.7 


83.6 
86.0 

87.7 


78.3 
81.6 
83.7 


73.1 

77.2 
79.9 


68.1 
72.9 
76.1 


63.1 
68.6 
72.3 


58.3 
64.4 
68.6 


53.6 
60.4 
65.0 


90 
100 
110 


96.1 
96.5 
96.7 


92.3 
93.0 
93.5 


88.7 
89.7 
90.3 


85.1 
86.4 
87.2 


81.7 
83.2 
84.2 


78.3 
80.0 
81.2 


75.0 
77.0 
78.3 


71.7 
74.0 
75.6 


68.5 
71.0 
72.9 


120 
130 


97.0 
97.1 


94.0 

94.2 


91.0 
91.3 


88.0 
88.5 


85.1 

85.7 


82.3 
83.1 


79.6 
80.6 


76.9 
78.1 


74.3 

75.7 



10 



11 



12 



13 



14 



15 



16 



17 



18 



40 
50 

60 



23.5 

38.7 
49.1 



16.5 
33.2 
44.6 



9.7 
27.8 
40.1 



3.0 

22.4 
35.7 



17.2 
31.4 



12.1 
27.1 



7.0 

22.8 



2.0 
18.6 



14.5 



70 
80 
90 



56.4 
61.5 
65.3 



52.5 
58.1 
62.1 



48.7 
54.8 
59.1 



44.9 
51.5 
56.1 



41.1 
48.2 
53.2 



37.4 
44.9 
50.2 



33.8 
41.7 

47.4 



30.3 
38.6 
44.7 



26.9 
35.6 

42.0 



100 

no 

120 
130 



68.0 


65.1 


62.3 


59.5 


56.8 


54.2 


51.6 


70.2 


67.5 


65.0 


62.5 


60.0 


57.5 


55.1 


71.8 


69.4 


67.0 


64.6 


62.3 


60.1 


57.9 


73.4 


71.1 


68.8 


66.6 


64.5 


62.4 


60.3 



49.1 
52.8 
55.7 
58.3 



46.7 
50.5 
53.6 
56.3 





19 


20 


21 


22 


23 


24 


25 


26 


27 


60 


10.5 
23.5 
32.6 


6.5 
20.2 
29.8 


2.6 
17.0 
27.0 














70 
80 


14.0 
24.3 


11.0 

21.6 


8.0 
19.0 


5.0 

16.4 


2.1 
13.9 


'ii.*4* 


90 
100 
110 


39.4 
44.4 
48.3 


36.8 
42.1 
46.1 


34.3 
39.8 
44.0 


31.9 
37.6 
42.0 


29.5 
35.5 
40.0 


27.2 
33.4 
38.0 


24.9 
31.3 
36.1 


22.6 
29.3 
34.2 


20.5 

27.4 
32.4 


120 
130 


51.6 
54.4 


49.6 
52.5 


47.6 
50.6 


45.6 

48.7 


43.7 
46.9 


41.8 
45.1 


40.0 
43.4 


38.2 
41.7 


36.4 
40.0 





28 


29 


30 




1 


1 


80 
90 

100 


9.0 
18.3 
25.5 


6.7 
16.2 
23.6 


4.4 
14.1 
21.7 


i 












110 
120 
130 


30.6 
34.7 
38.3 


28.9 
33.0 
36.7 


27.2 
31.4 
35.2 
















o 



C3 

c 
a 
■i-i 

V 

a 
'C 
X 



T3 

a 

a. 

'5 
cr 



o 

OS 

y 
U 

"3 

c 



H 

CO 
O 



o 
15 
O 



(0 

H 



TESTING 



539 



Table 84. Weight of Moisture per 1,000 Lb, of Dry Air, in Pounds. 

Barometer 29.92 In. 



Dry 
Thermometer 

op 


Vapor 
Pressure, 

Inches 

of 

Mercury 


Difference between Dry and Wet Thermometers, Deg. Fahr. 





1 


2 


3 


4 


5 


6 7 





0383 8 


0.5 
1.0 

1.8 


0.3 
0.8 
1.5 


0.0 
0.5 

1.2 










10 


0.0631 
0.1026 


1.3 
2.1 


0.2 
0.9 








20 


0.6 


0.3 




30 
40 
50 


0.1640 
0.2477 
0.3625 


3.4 
5.2 

7.7 


3.0 

4.8 
7.2 


2.7 
4.4 
6.7 


2.3 
3.9 

6.2 


1.9 
3.5 
5.7 


1.6 
3.1 
5.2 


1.2 

2.7 
4.7 


0.9 

2.3 
4.3 


60 
70 

80 


0.5220 
0.7390 
1 . 0290 


11.0 
15.8 

22.2 


10.4 
15.0 
21.2 


9.8 
14.2 
20.2 


9.2 
13.5 
19.3 


8.7 
12.8 
18.4 


8.1 
12.1 
17.5 


7.5 
11.4 
16.7 


7.0 
10.7 
15.8 


90 
100 
110 


1.4170 
1.9260 
2.5890 


30.9 
43.3 
59.6 


29.7 
41.6 
57.5 


28.5 
40.0 
55.4 


27.3 
38.4 
53.4 


26.1 
36.8 
51.5 


25.0 
35.4 
49.6 


23.9 
34.0 
47.8 


22.8 
32.6 
45.9 


120 
130 


3.4380 
4.5200 


82.5 
112.5 


79.7 
108.9 


76.8 
105.3 


74.1 
101.7 


71.4 
98.2 


68.8 
94.9 


66.3 
91.7 


63.9 
88.6 





8 


9 


10 


11 


12 


13 


14 


15 


16 


30 


0.6 
1.9 
3.8 


0.3 

1.6 
3.4 














40 


1.2 
2.9 


0.8 
2.5 


0.5 
2.1 


0.2 

1.7 


1.3 
3.4 






50 


0.9 


0.5 


60 
70 
80 


6.4 
10.1 
15.0 


5.9 

9.4 

14.2 


5.4 

8.8 

13.5 


4.9 

8.2 

12.7 


4.4 

7.6 

11.9 


3.9 

7.0 

11.2 


6.4 
10.4 
16.0 


2.9 
5.8 
9.7 


2.5 
5.2 
9.0 


90 
100 
110 


21.8 
31.2 
44.1 


20.8 
29.9 
42.4 


19.8 
28.6 

40.7 


18.8 
27.3 
39.1 


17.9 
26.2 
37.6 


16.9 
25.0 
36.0 


23.9 
34.5 
49.0 


15.2 
22.8 
33.0 


14.3 
21.7 
31.6 


120 
130 


61.5 
85.7 


59.3 
82.8 


57.1 
79.9 


55.1 
77.1 


53.0 
74.3 


51.0 

71.5 


68.9 
95.3 


47.0 
66.2 


45.1 
63.6 





17 


18 


19 


20 


21 


22 


23 


24 


25 


50 


0.1 
2.0 

4.7 


















60 


1.6 
4.1 


1.1 

3.6 


0.7 
3.1 


0.3 

2.6 










70 


2.1 


1.6 


1.1 


0.7 


80 

90 

100 


8.4 
13.5 
20.7 


7.7 
12.7 
19.7 


7.1 
11.8 
18.7 


6.5 
11.1 
17.7 


5.9 
10.3 
16.8 


5.3 

9.6 

15.8 


4.7 

8.9 

14.9 


4.1 

8.1 

13.9 


3.5 

7.4 

13.0 


110 
120 
130 


30.1 
43.2 
61.1 


28.8 
41.4 
58.6 


27.5 
39.7 
56.3 


26.3 
38.0 
54.1 


25.0 
36.5 
52.0 


23.8 
35.0 
50.0 


22.6 
33.5 
48.0 


21.5 
32.0 
46.2 


20.3 
30.5 
44.4 





26 


27 


28 


29 


30 










70 


0.2 
2.9 
6.7 
















80 
90 


2.4 
6.1 


1.9 
5.4 


1.3 
4.8 


0.8 

4.2 




— 


100 
110 
120 
130 


12.1 
19.2 
29.1 
42.6 


11.3 
18.1 

27.7 
40.9 


10.5 
17.0 
26.3 
39.2 


9.7 
16.0 
25.1 
37.5 


8.9 
15.0 
23.8 
35.9 









540 



TESTING 



Table 85. Weight in Pounds of One Cubic Foot of Saturated Air. 



Dry 




Barometric Pressure — 


-Inches 




Thermometer 
= F 


26 


27 


28 


29 


30 



10 
20 


0.0750 
0.07338 

0.071S0 


0.07788 
0.07620 
0.07456 


0.0S077 
0.07903 
0.07733 


0.0S365 
0.08185 
0.08009 


0.08654 
0.08468 
0.08286 


30 

40 
50 


0.07027 
0.06879 
0.06732 


0.07297 
0.07143 
0.06992 


0.07569 
0.07409 
0.07252 


0.078.39 
0.07675 
0.07512 


0.08110 
0.07942 
0.07773 


60 
70 
80 


0.0658S 
0.06442 
0.06297 


0.06^43 
0.06692 
0.06542 


0.07098 
0.06943 
0.06789 


0.07.353 
0.07193 
0.07a34 


0.07609 
0.07440 
0.07280 


90 
100 
110 


0.06146 
0.05991 
0.05828 


0.06388 
0.06228 
0.06060 


0.06629 
0.06465 
0.06293 


0.06870 
0.067a3 
0.06526 


0.07112 
0.06939 
0.06759 


120 
130 


0.05653 
0.05467 


0.05882 
0.05692 


0.06111 
0.05917 


0.06339 
0.06142 


0.06569 
0.06367 



Report of Complete Test 

TABLE 86 contains the items necessary for recording a complete evap- 
orative test. The sequence of the items has been chosen so as to keep the 
same numbers as were used in the short report, and so avoid confusion in 
explaining the different items. The actual form of report used should be 
that prescribed in the A. S. M. E. Code. 

Table 86. Complete Evaporative Test. 



Description of Boiler Rated H.P 

Located at 

Date of Test Duration Conducted by 

Coal, Kind size cost per lb., S. 

Grate, t)-pe area draft... 

Heating surface, boiler superheater economizer. 



(1 
(2 



(8 
(9 
(10 
(11 
(12 

(13 
(14 



Steami pressure, lb. per sq. in 

Percentage of moisture in steam or superheat. 

Factor of correction for quality- of steam 

Feed water temperature ""F 

Factor of evaporation 

Equivalent evaporation per hour, from and at 212'' F,, Ib... 
Equivalent evaporation per hour, from and at 212" F. 

per sq. ft. of heating surface, lb 

Percentage of rated capacit}- developed 

Percentage of moisture in coal 

Dry coal per hour, lb „ 

Dry coal per sq. ft. of grate surface per hour, lb 

Equivalent evaporation from and at 212° F. per lb. 

of dr}- coal, lb „.. 

Heating value per lb. of dry coal, B.t.u 

Efficiency per cent 



TESTING 



541 



(15 
(16 
(17 
(18 
(19 
(20 
(21 
(22 
(23 
(24 
(25 



(26) 
(27) 



(28) 



Barometer, in. of mercury 

Relative humidity of air for combustion, per cent- 
Temperature of air for combustion, °F 

Furnace temperature, °F 

Temperature of gases leaving boiler, °F 

Draft pressure in ashpit, in. of water 

Draft in furnace, in. of water 

Draft, leaving boiler, in. of water 

Refuse, per cent of dry coal 

Combustible in refuse, per cent 

Ultimate analysis of dry coal : 

(a) Carbon, per cent 

(b) Hydrogen, per cent 

(c) Oxygen, per cent 

(d) Nitrogen, per cent 

(e) Sulphur, per cent 

(f) Ash, per cent 

Fusion temperature of ash 

Analysis of flue gases by volume : 

(a) Carbon dioxide 

(b) Oxygen 

(c) Carbon monoxide 

(d) Nitrogen 

Heat balance based on dry fuel : 



Description 


B.t.u. Per cent 


(a) Heat absorbed by the boiler 

(b) Loss due to evaporation of moisture 

in coal 

(c) Loss due to heat carried away by 

steam formed by the burning of 
hydrogen 

(d) Loss due to heat carried away in the 

dry flue gases 

(e) Loss due to carbon monoxide 

(f) Loss due to combustible in ash and 

refuse 

(g) Loss due to heating moisture in air 

(h) Loss due to unconsumed hydrogen and 

hydrocarbons, to radiation, and un- 
accounted for 






(i) Total heating value of 1 lb. of dry coal. 

Item 13 


100.0 



Calculation of Complete Test 

In the following explanation, the item numbers are given at the com- 
mencement of the paragraphs : 

(1 to 14) These are the same as in the short report. 

(15) This is the average of the observations. It is to be converted 
into lb. per sq. in., and added to the gage pressure, item 1, to find the 
absolute pressure with which to enter the steam tables. 

(16) This item will be used in computing item g of the heat balance. 



542 TESTING 

(17) This is the average of the observations. It is used as the basic 
temperature in finding the losses set forth in items b, c, d and g of the 
heal balance. 

(18) This item is not used in the calculation of any of the results. 
It is necessary in researches into the transfer of heat by radiation and 
convection. It may also have some value in investigations as to any unusual 
formation of clinker in conjunction with item 26. 

''IP") This item is used as the higher temperature in finding the losses 
set forth in items b, c, d and g of the heat balance. 

(20, 21 and 22) These items are recorded for comparison with other 
tests. 

(23) This item is used to compute the weight of air required and the 
weight of gases, in computing items d and g of the heat balance. 

(24) This Item is used in the calculation of item f of the heat balance. 

(25) This is the laboratory report. 

(26) This Is the laboratory' report, and Is of service in investigating 
instances of unusual clinker formation. See also the remarks on item 18. 

{T^^ This is the average of the obser\-ations. and Is used In the calcu- 
lation of items d and e of the heat balance. 

The value of this analysis In promoting economv is discussed in Chapter 
16 on OPERATION. 

Heat Balance 

T— TAVING given attention to the rest of the items, the construction of the 
-*- ■'' heat balance can now be proceeded with. The heat balance may be 
made on the basis of coal as fired or of dr\* coal. The usual basis is dn,- 
coal, and the calculations will be studied In this manner. When the general 
method is understood, it is eas}' to make the heat balance in either of the 
waj-s mentioned. The letters at the commencement of the paragraphs are 
those of the items in the heat balance 28. 

(a) Heat absorbed by the boiler. Item 12 X 971.7. 

(b) Loss due to evaporation of moisture in coal. This moisture Is heated 
from the fire-room temperature, item 17, to 212 deg.. evaporated, and super- 
heated to the flue gas temperature, item 19. The latent heat of evaporation 
is 971.7, and the specific heat of the superheated steam is 0.47. 

The percentage of moisture. Item 9, is always reported on the weight 
of coal as fired. As the heat balance is based on dry coal, the moisture 
should be converted to this basis, though if the amount is small, the error 
is negligible. Thus 2 per cent of moisture becomes 2 X 100 98 ^ 2.04 per 
cent; and 10 per cent becomes 10 X 100 90 ^ 11.11 per cent. 

If coal containing 2 per cent of moisture Is fired at 60 deg., and the 
gases leave the boiler at 500 deg., then each pound of water takes up: 

212 — 60= 152.0 (Heating to 212 deg.) 

971.7 (Latent heat of evaporation) 
500 — 212 = 288, and 288 X 0.47 = 136.0 ( For superheating) 

Total = 1259.7 B.t.u. per pound. 

Each pound of dry coal is accompanied by 0.0204 lb. of water and this, 
multiplied by 1259.7, gives 26 B.t.u. 



TESTING 



543 



(c) Loss due to heat earned away by steam formed by the bnrniwj, of 
hydrogen. This is dealt with similarly to the moisture loss^ except that the 
steam resulting is 9 times the weight of the hydrogen. Assuming the same 
fire-room and flue gas temperatures as before, the loss will again be 1259.7 
B.t.u. per pound of steam formed. With dry coal containing 4 per cent of 
hydrogen, there will be 0.04 X 9 = 0.36 lb. of steam formed per pound of dry 
coal ; this multiplied by 1259.7 gives 453 B.t.u. 

{d) Loss due to heat earried aivay in the dry flue gases. This is nearly 
always the largest single item of loss. The temperature of the gas is raised 
from that of the fire-room, item 17, to the exit temperature, item 19. This 
rise of temperature multiplied by 0.24 (the assumed specific heat) is the 
B.t.u. loss for each pound of gas. From a fire-room temperature of 60 
deg. to a flue-gas temperature of 500 deg., the loss is 440 X 0.24 = 105.6 
B.t.u. per pound of flue gas. 

The weight of gas is computed from the flue gas analysis. An example 
is worked out in Table 87 to facilitate understanding the method. 







Table 87. Analysis of a Sample 


of Flue Gas. 




Volumetric j Molecular 
Analysis ! Weight 


Weights 


Per cent by 
Weights 


Carbon Oxygen 




Gas 


Per cent 


C=12 
0=16 

N=14 


100 X 

Items 

(II X III) under 

IV-^Total 
i of IV 


12/44ofC02 

and 
12/28 of CO 


32/44ofC02 

and 
16/28 of CO 


Nitrogen 


I 


II 


III 


IV V 


VI VII 


VIII 


CO2 

CO 


N 


14.0 
1.0 
3.0 

82.0 


12+ (16X2) =44 
12+16 =28 
16X2 =32 
14X2 =28 


616 
28 

96 
2,296 


20.29 
0.92 
3.16 

75.63 


5.53 

0.39 


14.76 

0.53 
3.16 


75.63 


Total 


100.0 




3,036 


100.00 


5.92 


18.45 


75.63 













The total amount of carbon in the gases (column VI) Is 5.92 per cent. 
Therefore the weight of dry gases is 100/5.92 = 16.89 lb. per pound of 
carbon. If the dry coal contains 80 per cent of carbon and the carbon lost 
to the ashpit is 2 per cent of the dry coal, then the carbon burned is 78 
per cent of the dry coal, and the weight of dry gas is 16.89 X 0.78 = 13.17 lb. 
per pound of dry coal. As shown above, 105.6 B.t.u. are used to heat 
one pound of dry gas from 60 to 500 deg., and 13.17 X 105.6 = 1390 B.t.u. 

Study of Table 87 will show that the molecular weights may be can- 
celed and the following formula derived for the weight of dry flue gas 



PV = 



1 1 CO, + 80, + 7 ( CO + iV,) 
3 {CO, + CO) 



X 



\^^ 1.833 j 



(67) 



where : 

W = Weight of dry gas per pound of dry fuel 
CO2, CO, O2, N2 ^ Percentages by volume in flue gas analysis 

C, S = Percentages by weight from ultimate analysis of dry fuel. 
C is the carbon actually burned, that lost in ashes and 
refuse being deducted. 







(U 



CO 

fl 

CO 

Wi 
(U 

o 

CO 

a> 
4-) 
a 

o 

ji 
O 



(U bfi 

'O CO 
(U o 

CO 

&>> 
E. ^ 



o 



CO 

CO 
(U 

C 

o 

(U 
(U 

u 
H 



TESTING 545 



(e) Loss due to carbon monoxide. When carbon is burned to COz, 
14,540 B.t.u. are evolved per pound, as against 4,350 B.t.ii. when burned to 
CO. The difference — 10,190 B.t.u. — is the loss due to each pound of carbon 
burned to CO. 

Table 87, column VI, shows that 0.39 lb. of carbon are burned to CO 
out of 5.92 lb. of carbon present in the gases. The proportion of carbon 
burned to CO is 0.39 X 100/5.92 -= 6.59 per cent; the carbon present in the 
gases is 78 per cent of the dry coal, so that 0.0659 X 0.78 = 0.0514 lb. of 
carbon are burned to CO per pound of dry coal. The loss per pound of dry 
coal is 0.0514 X 10,190 = 524 B.t.u. 

Without proceeding according to Table 87, the CO loss may be found 
from : 



(^+w) 



^ = cof+co '-^ • '^ + "T^^^ • ^ '"'^^ <^^ 



diere 



L := Loss in B.t.u. due to unburned CO 
10,190= Difference between the heat generated by burning 1 pound 
of carbon to CO2 and CO respectively, 
and the rest of the symbols are as in equation (67). 

With bituminous coals the presence of CO generally indicates the presence 
of unbnrned hydrocarbons also, so that the whole loss due to combustible in 
the gases may be assumed to be about double that due to the CO loss. With 
the anthracites, the CO loss will be the whole loss under this head. 

(/) Loss due to combustible in ash and refuse. The combustible in the 
ash is the main part of this loss. Sometimes the amount is assumed as the 
difference between the percentage of ash as weighed up during the boiler test 
and that found by the coal analysis. Or a representative sample of the ash 
can be analyzed; if it contains 20 per cent of combustible, and the ash is 10 
per cent of the dry coal, then 0.2 X 0.1 = 0.02 lb. of combustible in the ash 
per pound of dry coal. This can be considered as coke and valued at 14,540 
B.t.u. per pound. The loss will be 14,540 X 0.02 = 291 B.t.u. per pound of 
dry coal. 

(g) Loss due to heating moisture in air. With the readings of the wet 
and dry bull) thermometers the weight of moisture per pound of air may be 
found from Table 84. 

The weight of air per pound of dry fuel is : 

A = W + LhO — C (69) 

where : 

A = Weight of air per pound of dry fuel 
W = Weight of dry gas per pound of dry fuel 
H2O := Weight of water vapor in Item 28c, or 9 X Item 25^* 
C =: Weight of fuel per pound of dry coal in products of corn- 
Item 23 
bustion, 1 Yru\ — ■ 

Take the weight of gas per pound of dry coal as 13.17 as in item (/. Then 
tile weight of air will be : 

13.17 + 0.36 — 0.78= 12.751b. 

The weight of saturated vapor per pound of dry air at 60 deg. is found 
from the hygrometric tables to be 0.011 ; if the humidity is 75 per cent, the 
weight of vapor will be 0.011 X 0.75 = 0.008 lb. per pound of dry air. As the 
weight of air per pound of dry coal is 12.75 lb., the weight of -vapor in the 
air is 12.75 X 0.008 = 0.102 lb. per pound of dry coal. The rise in tempera- 
ture by the specific heat of the vapor is 440 X 0.47 = 207 B.t.u. per pound 
of vapor, and 207 X 0.102 = 21 B.t.u. per pound of dry coal. 



546 TESTING 



The loss due to humidity of the air is very small and is usually included 
in item h without separate determination. 

(h) Loss due to unconsumed hydrogen and hydroearhons, to radiation, 
and unaccounted for. The flue gas analysis rarely includes a determination 
of the unconsumed hydrogen and hydrocarbons, and the losses due thereto 
are usually included in this general item. 

The loss due to radiation is from 3 to 8 per cent of the heat value of 
the fueL When the boiler is driven hard and the temperature within the 
setting is high, the actual radiation loss is larger but is a smaller percentage 
of the heat generated ; whereas at ver>- low rates the actual loss is less, but 
is a larger percentage. Accurate measurement is impracticable : the radiation 
and '"unaccounted-for'" losses are usually lumped in one item, which is simply 
the difference between the sum of the rest of the items, and the heat value 
of the dr\- coal, item i. 

• A heat balance may now be made up as an example with the figures 
assumed, and Table 88 will illustrate the method. 



Table 88. Heat Balance. 



Destination B.t.a. i Per cent 



Heat absorbed by boiler = equivalent evaporation from 
and at 212 deg. per pound of dry- coal x 971.7(a) .... 

Loss due to evaporation of moisture in the coal (b) 

Loss due to heat carried away in the steam formed by 
combustion of hydrogen in the coal (c) 

Loss due to heat carried away in the dr\' flue gases (d) . . . 

Loss by incomplete combustion of carbon to CO (e) 

Loss due to combustible in ash and refuse (0 

Loss due to heating moisture in air (g) 

Loss due to radiation, unconsumed hydrogen and hydro- 
carbons, and unaccounted for (h) 

Total calorific ^-alue of one pound of dn.- coal, item 13 (i 13.850 100 



10,390 
26 


75.0 
0.2 


453 

1.390 

524 

291 

21 


3.3 
10.0 
3.8 
2.1 
0.2 


755 


5.4 



The second column is filled in first, and by dividing the different numbers 
of B.Lu. by their total, the percentages to be written in the third column 
are found. 

Efficiency 

THE efficiency shown by item a of the heat balance is the same as item 14. 
It is the combined efficiency- of the whole — ^boiler, superheater, furnace, 
grate — and is frequently called the overall efficiency. The consensus of 
opinion is that this is the only efficiency which should be reported. 

Attempts have been made to separate the overall efficiency into boiler 
efficiency and furnace cfficiencj-, and have resulted in much confusion. At 
present, it is absolutely impossible to decide what proportion of the losses 
due to unburned combustible gases and to radiat-on should be charged to 
the boiler and furnace respectively; and this proportion would verj- properly 
var>- according to the relative poorness of design of the boiler and stoker. 
While it would be valuable to know the furnace and boiler efficiencies sep- 
arately, it must be admitted that up to the present no method of finding 
them has been proposed which is not highly contentious. 



TESTING 547 



Accuracy 

THE absolute accuracy of the results of a boiler test even when conducted 
with the greatest care is doubtful, but there is as yet no common agree- 
ment as to what the probable limits might be. It is generally conceded, 
however, that there are several sources of indeterminate error, the more im- 
portant of which are discussed below. The limits of accuracy of a test 
might very reasonably be taken to be within plus or minus 3 per cent. 

One of the sources of probable error is the sampling of coal. Even when 
the greatest care is taken to obtain a representative sample, there may be an 
indeterminate error in ascertaining the heat value of the coal, even though 
the laboratory analysis is most reliable. With modern apparatus these 
laboratory determinations should be substantially correct as regards the 
sample tested ; but the question as to how truly the sample represents the 
whole, is always present and cannot be answered indubitably. 

Another is the moisture contained in the coal. As explained in the pre- 
ceding paragraph, the sampling is more or less uncertain. It is contended 
by some that if the attempt is made to determine the moisture during the 
test, the methods of drying and weighing are unreliable ; while others con- 
tend that though the moisture as determined in the laboratory is accurate 
so far as the sample delivered to the laboratory is concerned, this sample 
probably does not represent the bulk of the coal actually burned since there 
must inevitably have been more or less loss of moisture during the collec- 
tion, preparation and handling of the sample. 

Similarly, it is problematical whether the samples collected for the 
determination of the moisture in steam and for gas analysis are representative 
of the bulk, although the testing of the samples obtained may be quite 
accurate. 

It is not unusual for heat balances to be reported to the nearest B.t.u. 
and to the nearest one-tenth of 1 per cent. But the present state of the art of 
boiler testing does not provide means for attaining anything like this ac- 
curacy. In general, results should be reported only to the nearest significant 
figure. Reporting results of any kind in small units is likely to convey an 
erroneous idea as to the real accuracy of the figures. 

It is therefore quite logical in the case of guarantee tests, that a sub- 
stantial compliance with the guarantee be accepted as full compliance there- 
with, although preferably a limit of tolerance should be agreed upon before- 
hand l)y the parties to the test. The amount of this tolerance might well 
bear some relation to the care exercised in arranging the details of the test. 

Steam Consumption by Auxiliaries 

THE steam or power used in generating forced or induced draft, reducing 
smoke by means of steam jets, driving stokers, atomizing liquid fuel, 
oil heaters, oil pumps, and so forth, should be determined and specifically 
reported. No deductions on this account are to be made ; but they may 
conveniently be reduced to a percentage of the steam generated. 

The method of finding the steam consumption of auxiliaries by means 
of the rate of fiow of steam through a nozzle or an orifice in a thin plate is 
described on page 421. 

Soot 

OOOT accumulations are seldom accounted for, as the quantity is small 
^ during an ordinary trial. The quantity of combustible carried off in the 
gases as smoke is determined only rarely. A prepared surface of 21 sq. in. in 
area suspended in a stack has l^een found to collect 9 to 184 milligrams 
per hour. 



548 TESTING 



Smoke 

NO wholly satisfactory methods for either quantitative or qualitative smoke 
determinations have yet come into use, nor have any reliable methods 
been established for definitely tixing even the relative density of the smoke 
issuing from chimneys at different times. One method commonly employed, 
which answers the purpose fairly well, is that of making frequent visual ob- 
servations of the chimney at intervals of one minute or less for a period of 
one hour and recording the observed characteristics according to the degree 
of blackness and density, and giving to the various degrees of smoke an 
arbitrarv percentage value rated in some such manner as that expressed 
in Table 89. 

Table 89. Smoke Percentages. 

Dense black 100 

Medium black 80 

Dense gray 60 

Medium gray 40 

Light gray 20 

Very light - - 5 

Trace - .- 1 

Clear chimnev 



The color and density of smoke depend somewhat on the character of 
the sky or other background, and on the air and weather conditions obtaining 
when the observation is made, and these should be given due consideration 
in making comparisons. Observations of this kind are also subject to errors 
of judgment. Nevertheless, these methods are useful, especially when the 
results are plotted according to the percentage scale determined on so that 
a graphic representation of the changes can be shown. 

Various forms of charts and clouded glass arrangements for comparing 
and fixing smoke densities have been proposed and to some extent used : 
but these have proved more or less unsatisfactory and they are subject to 
personal errors, and to sky, wnnd, and weather conditions, the same as the 
simpler method above described. 

Among the chart methods referred to, the use of the Ringelmann smoke 
chart is perhaps the most familiar. This is shown in Fig. 231. 

To use this chart, four cards are ruled like those shown, though covering 
a much larger area, and placed in a horizontal row about 50 ft. from the 
observer, and in line between him and the chimney, together with two other 
cards, one of which is white and the other solid black. The observer glances 
rapidly from the chimney to the cards and judges which one corresponds 
with the color and density of the smoke. He makes these observations every 
minute, or oftener if desired, recording the number of the card representing 
the character of the smoke at the instant of observation. The results are 
then plotted on a chart, and the variations shown graphically. 

The lines in cards 1 to 4 are respectively 1, 2.3, 2).7, and 5.5 mm. thick, 
and the spaces 9, 7.7, 6.2), and 4.5 mm. The lines should be made with black 
India ink. 

A convenient method of recording and presenting smoke reports is 
illustrated on page 65. 

Another method of smoke determination consists in the use of a nar- 
row flat metal plate suspended in the flue, the character of the smoke being 
indicated by the amount and qualit}' of the soot and dust deposited upon the 
plate in a given time. This method, like others, is useful in furnishing a 
means of comparison in different cases rather than a means of exact de- 
termination. 



TESTING 



549 













































































































• 






































































































































■ 
















































No. 1. 










" 


— 


" 






"" 
















































































































































































































































































No. 2. 




No. 3. No.4- 

Fig. 231. Ringelmann Smoke Chart. 



550 



TESTING 



Among tlie latest methods brought out for indicating and recording 
the density of smoke is one depending on the variations in the electrical 
conductivity of the metal selenium due to variations in the intensity- of light 
shining upon it. Openings are provided on eitlier side of the tiue directly 
opposite each other. The selenium is located at one opening and a strong 
light at the other. The intensity of the light ra^'s falling on the selenium 
varies with the densit>' of the smoke. A milliampere meter in circuit with 
the selenium cell registers the variations. 

Liquid and Gaseous Fuels 

Tests v.-ith liquid and gaseous fuels follow the same general lines as 
those with solid fuels. Liquid fuel tests are reported on weight of fuel as 
in solid fuel tests, while gas tests are commonly reported on a volumetric 
basis. 




West Side Station, Denver Gas & Electric Co., Denver, Colo. Part of 
10,000 H. P. of Heine Standard Boilers and Heine Superheaters. 



551 



CHAPTER 16 



OPERATION 

THE methods and apparatus concerned in the operation of boiler plants 
may be divided into two classes — necessities and money savers. The 
necessities, v^ithout which the plant either cannot be operated at all or 
cannot be operated with safety, will generally be considered first. Discussion 
of the money savers, which either reduce the cost of operation or assist in 
reducing it, will follow. The latter might be divided further into two classes 
— those which directly save money such as feed water heaters and coal 
conveyors, and those which show where waste occurs such as CO2 recorders 
and coal weighers. 

Boiler Fittings 

' I 'HERE are several necessary items of equipment which must be attached 
-'■ to a steam boiler before it is placed in service, among which are a water 
column, safety valves, steam gage and blow-ofif valves. 

Water Column. The water column usually consists of a cast iron body 
connected at the bottom with a pipe to the boiler below the water level and 
at the top to the steam space of the boiler. It is provided with three or more 
trycocks, one placed at about the mean or normal v/ater line, and the others 
above and below. The gage glass is connected through gage cocks at its top 
and bottom to the water column ; and if both gage cocks are open, the water 
will stand in the glass at the same height as it is in the column and in the 
boiler. Both gage glass and water column should be provided with drain 
cocks, so that they may be blown out. If valves are placed in the pipes 
connecting the water column with the boiler, particular care must be taken 
to lock them or otherwise prevent absolutely their closure by unauthorized 
persons. Long pipe connections from the boiler to the water column should 
be avoided, as there is always the possibility of such long runs of pipe be- 
coming clogged with sediment or scale, thus causing the water' column 
to become inoperative. In these pipes crosses are preferable to elbows, for 
when the plugs are removed, the pipes can easily be cleaned and looked 
through. 

Fig. 231 shows the type of water column used as standard equipment on 
all Heine boilers. This column is provided with copper floats which operate 
a whistle when the water level is too high or too low. 

Safety Valves. The function of a safety valve is to prevent the pressure 
in the boiler to which it is attached from rising above a definite point called 
the working pressure. The working pressure of a new boiler is, of course, 
dependent upon the design and thickness of materials used in its construction. 
The working pressure of a boiler which has been in service for some time 
is dependent upon its age and physical condition, and is usually governed by 
the report of a municipal or insurance boiler inspector. 

The A. S. M. E. Boiler Code (1918) requires that the safety valve capac- 
ity for a boiler shall be such that the safety valve or valves will discharge 
all the steam that can be generated by the boiler without allowing the pres- 
sure to rise more than 6 per cent ajjove the maximum allowable working 
pressure, or more than 6 per cent above the highest pressure to which any 
valve may be set. The total relieving capacity of the safety valve or valves 



552 




1000 H. P. Heine Standard Boiler in course of erection at the 
Walter Reed Hospital, Washington, D. C. 



OPERATION 



553 



required on a boiler shall be determined on the basis of 6 lb. of steam per 
hour per sq. ft, of heating surface for water tube boilers. Charts for de- 
termining safety valve sizes are given in Chapter 8 on PIPING. 



'Steam 




Fig. 231. 



Wafer 
Reliance Water Column equipped with Self-Closing Gage. 



When two or more safety valves are used on a boiler, they may be 
either separate or twin valves, which are made by mounting individual 
valves on a Y base, j- uplex, triplex or multiplex valves are those which 
have two or more valves in the same body or casing. 

The blow down, or dih'erence between opening and closing pressure of the 
safety valve shall not be more than 4 lb. on boilers carrying less than 100 
lb. gage pressure, not more than 6 lb. on boilers carrying between 100 lb. 
and 200 lb. pressure, and not more than 8 lb. on boilers carrying over 200 
lb. pressure. 

The use of weight lever safety valves or dead weight valves is not per- 
mitted under the A. S. M. E. Code, hence only spring loaded pop safety 
valves will be described Here. 

Fig. 232 illustrates a typical pop safety valve for use with saturated 
steam, in which the boiler pressure acting upon the under side of the valve 
is resisted by the helical spring. When the boiler pressure exceeds the 
spring resistance, the valve lifts from its seat and the steam escapes into 
the atmosphere. 



554 



OPERATION 



The valve is provided with a skirt which becomes rilled with steam when 
the valve is open, so that the efiFective area of the valve is increased. As 
soon as the valve lifts, this increased area immediately takes effect ; and the 
greater load on the spring compresses it more than would be the case with 
a plain valve, and the valve opens wider. Once open, the valve will remain 
open while the pressure drops below that which opened it, because of the 
effect of the increased area. The pressure per sq. in. on the added area is 
less than the boiler pressure, and is dependent upon the freedom with which 
the steam can escape from under the skirt. Passages connect this part with 
an annular space called the ' huddling chamber." and this chamber is pro- 
vided with an adjustable outlet. If the huddling chamber outlet is closed, 
the pressure under the skirt will be greater, and the boiler pressure will 
drop ver>- low before the spring can close the valve. If the huddling chamber 
outlet is wide open, the pressure in it and under the skirt will be small, and 
the valve will close with ver>' little drop of boiler pressure. The difference 
of pressure between that necessar>^ to open the valve and that at which 
the spring can close it, is called the ''blow down,"' and is adjusted by con- 
trolling the huddling chamber outlet. 




Fig. 232. Ashton Pop Safety Valve for Saturated Steam. 



It has been explained how the effect of the skirt is to cause the valve 
to open wide immediately upon opening at all. In closing, this action is 
reversed, for when tlie boiler pressure drops sufficiently to allow the spring 
to begin closing the valve, the pressure under the skirt drops and allows 
the spring to close the valve further, so that the action is cumulative and 
the valve closes quickly. Owing to the rapidity with which these valves open 
and close, they are called "pop" valves. 

The valve may be opened to discharge at any pressure less than the 
relieving pressure by operating the hand lever, 



OPERATION 



SS5 



Every superheater should be equipped with a safety valve at its outlet, 
set to blow at a lower pressure than the boiler safety valves, in order that a 
flow of steam may be maintained through the superheater if fo*" any 
reason the main steam flow is stopped ; and this will avoid damage to the 
superheater tubes by burning. 

Fig. 233 shows a type of valve designed for superheated steam service. 
The spring is exposed to the air, so that high temperature steam does not 
affect its elasticity by coming in contact with it. 




Fig, 233. Consolidated Pop Safety Valve for Superheated Steam. 



Steam Pressure Gages. Every boiler must be equipped with a steam 
gage, which may be connected directly to the boiler steam space or to the 
water column or its steam connection. 

These gages are generally of the round-pattern, indicating type. They 
consist mainly of a pressure element in the form of a tube spring or a dia- 
phragm, and of a movement to operate the indicating mechanism. The styles 
differ chiefly in the details of construction, such as material, mountings, 
trimmings and finish. 

The Bourdon pressure element is an oval metal tube, closed at one 
end and bent in an arcuate form to give the single or double spring, as in 
Fig. 234. The free end of the tube is connected by one or more levers 
to a toothed sector or segmental rack, which actuates a small pinion on the 
pointer shaft. Lost motion is taken up by a hair spring attached to this shaft. 



556 



OPERATION 



For marine and portable work or in stationar3- installations where 
vibrations would jar the sensitive mechanism, the double-tube gage is recom- 
mended. This gage is not so easily affected by rapid fluctuations of pres- 
sure. The r«-o free ends of the pressure tubes are connected to a multi- 
plying mechanism similar to that in the single-tube gage, but the needle 
movement is much greater. 






Indicating 
Single Tube. Dial. " Double Tube 

Fig. 234. Bourdon Tube Steam Gages. 



When measuring pressure, gages snow the dinerence c^tween the inside 
pressure actuating the device, and the pressure on its outside. Therefore. 
when the gage indicates zero, the pressures inside and outside of the spring 
are the same; when it indicates 50 lb., then the pressure inside the spring is 
50 lb. greater than the pressure on its outside. The absolute pressure is 
the sum of the atmospheric pressure (14.7 lb.) and the gage reading; thus 
50 lb. gage is equivalent to 64^J lb. absolute. Pressure is usualh* expressed in 
pounds per square inch. 

In selecting a gage, the size and imit of the scale required should be 
specified, and the scale selected should not exceed one and one-half times 
the working pressure. Roimd pattern gages used on the steam plant, range 
from 3 to 12-in. diameter. The dials of indicating gages are usually silver 
finished brass, having figures and graduations filled with black enamel; or 
they may be black with silver figures. The casings are iron, brass or nickel- 
plated. 

Gages should be located so that they are accessible, can be easily read. 
and so connected as to insure correct readings. Standard gages have a 
J4 in, pipe-thread male connection and are generally provided with a stop 
cock. For dark or obscure places, illuminated dial gages should be usei 

Gage tubes may become softened when subjected to temperatures of 
more than 150 deg.. so that steam or ver>- hot water should not come in 
direct contact with the tube. A goose-neck siphon or loop. Fig. 235. is used 
to maintain a protective water seal between the gage and the steam supply. 

^^'hen the gage is exposed and subject to freezing, a pet cock. Fig. 235d, 
should be provided for draining the water from the siphon. Freezing might 
burst the connection or damage the gage spring. This pet cock should not 
be opened when tke pressure gage is in ser\-ice. as then the water seal would 
be lost and the gage tube be liable to be damaged by contact with the steam. 

If a gage is placed below a pipe line. Fig. 235e, allowance must be 
made for the head of water in the seal to obtain correct readings. Such 
a correction can be made by multiplying the head of water in feet by .433. 
thus reducing it to lbs. pressure per sq. in., which should be deducted from 
the gage readings. 



OPERATION 



557 



Gages should be attached securely to minhnize the effects of vibration. 
Repeated jarring will cause wear of the rack and pinion, resulting in in- 
accurate pressure indications. Gages subject to vibration, or placed high 
up and in hot boiler rooms, should be frequently tested. As the spring of 
the gage has only a slight motion, the least interference with it will produce 
a noticeable error because of the greater movement of the needle or pointer. 






b. c. d. 

Fig. 235. Siphons for Steam Gages 




A gage can be calibrated by comparison with a standard test gage, or 
by trial on a dead weight tester, or on a mercury column tester. Where 
testing devices are not available, as in the small plant, gages should be 
sent to the factory. A typical dead weight tester, Fig. 236, consists of a 




Fig. 236. Dead Weight Gage Tester. 



stand on which is mounted an oil reservoir, plunger pump and cylinder 
fitted with a piston to receive the weights. The gage to be tested is attached 
to a three-way cock. Each test weight is marked with the pressure in 
pounds per square inch that it will show on the gage. The weights are 
placed on the disk, one at a time ; and they should be whirled while taking 
the reading, so as to eliminate the error caused by the friction of the 
plunger. If the gage is at variance with the dead weight applied, it may 
be corrected by removing the pointer with a gage-jack and pressing it back 
on the spindle at the proper indication. 






; ;■ IB 13 1] 

9 5! ia Eg in 
I 11 Bl 11 II 
i QS II II ]} 

i 11 10 II i] 
i 



Union Central Life Insurance Building, Cincinnati, Ohio, equipped with 

Heine Standard Boilers. 




559 



Fig. 237. Everlasting Blow-off Valve. 




Fig. 238. Yarway Seatless Blow-off Valve, 



560 



OPERATION 



Blow-off J^alvcs. All boilers should be equipped with one or more blow- 
ofiF pipes, with one or more cocks or valves on each pipe. The A. S. M. E. 
Code (1918.1 provides that blow-off piping shall not be less than 1 inch or 
larger than lYz inches, and that globe valves should not be used. The re- 
quirements of a good blow-off valve are that it shall provide a clear passage 
for water, mud and scale, and that it shall open easily and close tightly. 

Fig. 237 illustrates the Everlasting Blow-off Valve, which consists of a 
top and bottom bonnet and a disc which swings between seats on the faces 
of the bonnets. The disc is actuated hy a lever. 

Fig. 238 illustrates the Yarway Seatless Blov,-:f \'alve. A plunger V 
is operated by a hand wheel and screw. In closing the valve, the shoulder 
S on the plunger V engages the loose follower gland F. compressing the 
packing P above and below the port, thus making a tight closure. 

Fusible Plugs, see Tig. 239, are intended to protect a boiler in case 
of low water. At best, these plugs are unreliable, but the law in some 
states requires their use, even in water tube boilers. 



TiHiiVi Typ^" 



Oatsde^ ypo *- 




Fig. 239. Fusible Plug: 



The fusible plug consists of a brass or bronze fitting which may be 
screwed into the shell, furnace crown sheet, or waterleg of a boiler. The fit- 
ting is bored out and filled with pure tin or some composition metal which 
has a melting point but little above the temperature of the steam in the 
boiler. The metal of the plug transmits the heat to the water so rapidly that 
its temperature does not rise if it is covered with water; but if the water 
level falls below the plug, the fusible metal in the core will melt out, allowing 
the steam to escape. If heard or noticed, this will serve as an indication of 
low water. 

Methods of Hand Firing Coal 

HAXD-FIRIXG is not onl\- hard work, but requires considerable judg- 
ment and skill if waste of coal is to be avoided. The method of firing 
depends upon the kind and quality of coaL 

Bituininous Coal. Inasmuch as bituminous coals varj- widely in compo- 
sition, it is difficult to state definite rules for handling which will fit all 
cases. The most suitable method of firing a particular coal is best determined 
by experimenting with it, and a careful fireman soon learns how to p/oduce 
the best results. 

There are three general 53-5tcm5 of f.ri::^. k:.c ..:: as alternate, spread- 
ing and coking. 

In the alternate system, fresh coal is fired nrs: f r : - vr ' - ?. :e 

then on the other, or through alternate doors rrr ire . :rr : .::: 

two, so that the entire fire is not blanketed with green coaL This sj'stem 
is used where the grates are wide or when two or more furnaces have a 
common combustion chamber. 



OPERATION 561 

The spreading system consists in charging a small amount of coal, 
spreading it in a thin layer over the entire grate at each firing ; usually it 
is spread from the bridge wall toward the door. Although it means more 
work for the fireman because the furnace must be fired frequently, the use 
of this system is increasing. It gives an air supply which is always more 
nearly proportional to the fuel supply. 

In the coking system, the fresh coal is piled up on the dead plate or on 
the front of the grate, so that the mass can become nearly or wholly coked. 
It is then pushed back toward the bridge wall, and spread evenly over the 
grate to make room for the new charge. When no dead plate is provided, 
about one-third of the grate at the front is left bare and receives fresh coal 
at each firing. This system is adapted to furnaces in which the gases pass 
horizontally over the fire. 

The spreading and alternate methods, as compared with the coking 
system, give higher efficiency, higher CO2 and lower temperature of exit 
gases. Because of the greater uniformity in furnace temperatures, steam 
is generated more uniformly. In the coking method less of the refuse appears 
as clinker and more as ash, but the combustible lost through the grate is 
about the same in the three methods of firing. The amount of slicing and 
raking is equal with all three, but the coking method also requires time and 
labor for leveling. 

The spreading and alternate methods of firing are widely used in hand 
firing non-caking and high volatile bituminous coals. In the alternate 
method the volatile matter given off by a fresh change of green coal on the 
one side of the grate, is mixed with some air which has been heated by 
passing through the fuel bed on the other side; but care must be taken to 
make provision for thoroughly mixing the gases from the two sides of the 
fire, and there is the difficulty of getting one side of the fire heavier than 
the other. Spreading over the complete fuel bed is perhaps more extensively 
used than even the alternate method, and has the advantage over the 
alternate method that the whole fuel bed can be kept of more uniform 
thickness, thus minimizing the possibility of holes occurring in the fire. 

The coking method is most applicable to those bituminous coals which 
cake or melt and run together upon heating. With this method the hydro- 
carbons must pass over the hottest part of the fire which is near the bridge 
wall, on their way to the boiler heating surface. The back part of the fire 
should be kept thicker, as the character of the coke bed is much more open 
here than at the front. 

Two disadvantages of the coking method of firing are that the fire doors 
must be kept open relatively long in order to work the fire, which results 
in large quantities of excess air; and the fire is being continually disturbed, 
a fact which will result in excessive clinkering with coals containing fusible 
ash. 

Following are a few general rules which have been formulated by the 
Coal Stoking and Anti-Smoke Committee of the Illinois Coal Operators' 
Association for the hand-firing of Illinois and Indiana coals. 

(1) Break all lumps, and do not fire coal into the furnace of a size 
larger than the fist. Large pieces do not ignite quickly and their presence 
results in the formation of holes in the fire, with consequent losses due to 
excess air. 

(2) Keep the ash pits bright at all times. If they become dark it is 
an indication that the grates are becoming covered with clinkers and that 
the fire needs cleaning. 

(3) Do not fire the coal in heaps on the grate unless filling up a 
hole. Spread the coal as it leaves the lip of the shovel. 



562 OPERATION 



(4) When firing, spread the coal from the bridge wall forward. 

(5) Do not allow the fire to burn dull before charging. 

(6) Do not allow holes to form in the fire. Should one form, it should 
be filled by leveling. 

(7) Regulate the draft bj- the ash pit doors rather than b}- the manipu- 
lation of the stack dam.per. When the stack damper is closed the intensity 
of the draft is diminished, but by closing the ash pit doors the air supply 
is reduced. 

Referring to rule (7), general opinion is against regulating the draft 
by the ashpit doors. The air supph- is reduced, whether it is the damper 
or the ashpit doors that are partly closed. Closing the ashpit doors is 
generally believed to result in undul}^ heating the grate bars ; and it reduces 
the boiler efficiency by causing an increase in the leakage of air through 
defects in the setting. 

Anthracite. Anthracite should be fired by the spreading method, in 
small quantities and at frequent intervals. For large sizes of anthracite 
such as "stove" or "egg," almost any type of hand-fired furnace is suitable. 
However, the larger sizes of anthracite are now almost exclusively used for 
domestic purposes, and because of their high cost are but little used under 
steam boilers. The smaller grades of anthracite do, however, find extensive 
use as boiler-fuel, and their successful burning depends upon several factors. 

The small sizes of anthracite pack closely together on the grates, which 
makes the employment of a strong draft necessarj^ to secure the proper 
amount of air for combustion. Mechanical draft is usuall}^ employed, which 
is obtained by the use of steam jet blowers or by fans. As the fine grades 
of anthracite run higher in ash than the larger grades, there is considerable 
tendency toward clinker formation; and the employment of steam jet blowers 
for forced draft is desirable, as the introduction of steam into the ash pit 
decreases formation of clinker. 

It is desirable to disturb the fuel bed as little as possible with the firing 
tools. With a little practice, the fuel can be spread very thinh*. The fire 
should be kept of even thickness, and if necessary it may be levelled occa- 
sionally with a tee-bar. This can be a light tool made of a length of ^ 
or 1 in. pipe screwed into the branch of a tee, with pieces of pipe about 6 in. 
long screwed into the "runs." The fire is simply to be leveled with this 
tool, and not stirred up. Some firemen get good results by leveling the fire 
with a tee-bar between each firing. 

There is a limit to the forced draft pressure when small anthracites are 
burned, owing to the liability of lifting the fuel off the grate. This makes 
holes in the fire and carries some of the fuel into the combustion chamber 
and flues. Owing to the necessarily slower rate of combustion, the grate 
area for small sized anthracite is made larger than for bituminous coal in 
order to develop the same horsepower. The relation of grate area to boiler 
heating surface to develop the rated capacity of a boiler is given in Table 89. 



Table 89. Relation of Grate Area to Boiler Heating Surface. 
Size of Coal Ratio 



Xo. 1 Buckwheat 


1 to 40 


Xo. 2 


1 to 35 


Xo. 3 


1 to 30 


Xo. 4 


1 to 25 



OPERATION 



563 



On account of the large amount of ash in small hard coal, there will 
be a considerable depth of ash on the grate just before cleaning. The ashpit 
pressure is small just after cleaning, but as the ash thickens on the grate, 
the pressure must be greatly increased to maintain an even combustion rate. 
Therefore, forced draft blowers should be chosen which have characteristics 
showing that their efficiency is maintained over a wide pressure range. 

The "free burning" varieties of anthracite are burned satisfactorily when 
the above directions are followed. But with the harder coals — those con- 
taining very little volatile matter — it is usually necessary to mix from 10 to 
15 per cent of bituminous coal. The bituminous coal should be fine "slack," 
not lumpy. 

Tools for Hand Firing. The hoe, slice bar, rake and shovel are the 
necessary hand tiring tools, and Fig. 240 illustrates those designed for a 
6 ft. grate. 




1 Standard pipe 
HOE 



1 'round bar 
welded to end of 
pipe and blade 
riveted to It 




-p--tr-N\ /Welded 




-6'6- 



->y 2'6 



Welded ^ 



IV4 Standard pipe 
SLICE BAR 



-^^ 



■X* 



"iW' 



^i 




elded 



I Standard pipe 
RAKE 



Fig. 240. Tools for Hand Firing. 




For best results in hand-firing, the equipment must be so arranged 
that the shovel and other firing tools can be handled freely without hitting 
bumps and rivets. This implies sufficient firing space, a smooth floor to 
receive the coal, or still better, a hand or industrial coal car similar to the 
type shown in Fig. 241. 

In the firing procedure recommended by the Bureau of Mines, the 
fireman takes the position indicated in Fig. 242, in which he can see the thin 
spots in the fire and can throw the coal on without exertion. He stands 
4>^ to 5 ft. in front of the furnace at about 12 to 18 in. from the center 
line of the firing door. The coal pile is about 2 ft. away. 

If the coal is less than 6 to 7 ft. from the boiler front, the fireman is 
crowded. To avoid the intense heat, he stands to one side of the door, and 
throws the coal in by guess. The room for handling the scoop is not suffi- 
cient, so it travels in the arc of a circle, scattering some coal in its path, and 
dumping the remainder in a heap on the dead plate or on the grate just 
inside of the firing doer. The result is an uneven lire that requires raking 
and spreading over the grate. 




■i-i 







P3 


c 




'" 


-0 


m 


u 


u 


CO 


u 


TJ 


rz» 


C 





CO 


CQ 


4-1 




«J 


C3 


c 


cu 


u 


jz 


K 


&£ 


(m 


u 









^ 

7S 


CU 


4-1 




4-) 


ffi 




,o 


d 


o 



t" T/ 



J3 J= 



t: o 

o " 



2 o 

"■*-> ■*-• 

4-' 

C o 

.- "-J 

c 

£ S 

a. o 

3 



u 
CQ 



OPERATION 



566 



For economy, coal should be burned rapidly and at high temperatures. 
This means light firing or the frequent charging of small amounts of coal 
to prevent the thin places from burning through and admitting too much 
excess air. The amount of coal and time of firing depend upon the grate 
surface for the available draft. A draft of 1 in. in the uptake v^ill give 
good results with 2 to 2^ lb. of coal to a square foot of grate at each 
firing. A boiler with a grate 6 by 8. ft. would then require six to nine 
shovelfuls of coal at each firing period, about every 5 minutes. For a higher 
draft the interval might be 3 minutes, and for a lower draft the firing time 
might be 8 minutes. 

The facilities for handling, care in charging and cleaning fires, and the 
suitability of the type of grate to the fuel burned — all may cause loss or 
waste of coal. With poor facilities or management the total may run as 
high as 10 per cent of the coal consumed, while under fair operation the 
loss will average from 2 to 3 per cent. 




Fig. 241. Steel Coal Cars. 





\-Z'-\ 



•---4' to 5'-—^ 
Fig. 242. Proper Position for Hand-firing. 



566 OPERATION 

The^ thickness of fuel-bed required depends to a large extent upon the 
grade of coal, available draft, firing periods and the experience of the fire- 
man. For a given operating condition and boiler setting, the thickness giving 
maximum efficiency can be determined by test. If the fuel-bed is too thin 
excess air will result. If it is too thick the air supply will be insufficient 
for proper combustion. In either case the boiler efficiency will be decreased. 
Generally a thin fire is to be favored, but with coarse coal the fire bed 
should be thicker. For the larger sizes of anthracite a fuel-bed of 6 to 10 in. 
can easily be carried ; a 2-in. bed will give good results with barley and rice 
coals. The free-burning bituminous coals can be easily handled with a 6 
to lO-in. bed ; the poorer grades give good results with a fuel-bed 4 to 6 in. 
thick. 

Lignite. Lower grades of lignite disintegrate and crumble readily when 
heated. The packing of this finely divided fuel on the grate increases the 
resistance of the fuel bed to the flow of air, hence a high draft pressure 
is required for even moderate rates of combustion. This crumbling causes 
intense combustion near the grate where the air enters, and the high tem- 
perature at this point, coupled with the low fusion point of the ash, results 
in the formation of clinkers. The fuel bed should be disturbed as little as 
possible during firing, because of this tendency to form clinker. Special 
types of overlapping grates with small air spaces should be used to prevent 
the disintegrated lignite from sifting into the ash pit. The thickness of the 
fuel bed may vary from 4 to 8 inches with natural draft, and up to 20 
inches with forced draft in the semi-producer tx-pe of furnace. Either the 
alternate or spreading type of firing may be used with lignite. 

Wood. Cord wood or slabs may be successfully burned on herring-bone 
grates with natural draft. When stacked in a furnace they form an open 
fire through which the friction draft loss is slight, and hence the fuel bed 
may be as much as from 2^4 to 3 feet in depth. Double-deck fire doors on 
the fire-fronts are convenient for feeding slab wood. 

Hog wood, or the refuse resulting from the maceration of logs and 
mill ends in a hogging machine, may be fed to the grates through chutes 
or by hand. It is generally burned in a Dutch oven on herring-bone or 
Tupper grates. The fuel bed may. be from two to four feet deep. Care 
should be taken to avoid too much excess air coming in through fuel 
chutes or by parts of the grates being uncovered. The bed of fuel should 
not be disturbed with firing tools of any kind ; but even then a large amount 
of unconsumed wood particles are carried away. 

Forced draft under the grates is not desirable, because of increasing the 
amount of "fly ash" and unconsumed particles of wood carried up into the 
breechings, etc., where secondary- combustion may cause damage. 

Excellent results are being obtained in burning this fuel on Laclede- 
Christ\- Chain Grate Stokers under Heine standard boilers. Compared with 
hand operation, these stokers give much higher boiler efficiency and entirely 
eliminate smoke and the carriage of unburned particles out of the furnace 
and combustion chambers. 

Wet or green sazidust is satisfactorily burned on hollow blast grate bars 
with forced draft. Inasmuch as the character of the sawdust as regards its 
resinous properties, moisture content and size of particles, vary in different 
localities, no general thickness of fire can be recommended, but usually it 
will be less than twelve inches. It is preferable to fire the sawdust over the 
grate surface evenly by hand. Heaps or cones formed when the sawdust is 
fed into the furnace through chutes should be constantly leveled. 

Shavings and fine dust from polishing machines are not usually available 
in sufficient quantities to burn alone. They are generally used in conjunction 
with coal fired grates, often set in an extension furnace. As this material 



OPERATION 567 



is generally very dry, care must be taken that there is a vacuum in the fur- 
nace, for if not, the furnace brick work and cast iron fronts will be damaged 
by the intense heat. 

Tan Bark. Tan bark may be satisfactorily burned in a Dutch oven or 
extension type furnace equipped with horizontal or inclined stationary grates. 
The grates usually have from 20 to 30 per cent air space, with the actual 
opening between bars not more than '/le to ^A inch, thus preventing the tan 
bark from falling into the ash pit. The ratio of grate surface to boiler 
heating surface is generally about 1 to 30. 

The thickness of fuel bed varies with the character of the bark, furnace 
design and available draft. In the usual practice, the tan bark feed chutes 
are located in the top of the extension furnace arch, and the material builds 
up on the grates in the form of cones. These cones will vary in depth, and 
where they meet will be from 6 to 18 inches. 

Tan bark is sometimes fired with bituminous coal in a Dutch oven fur- 
nace equipped with dumping or shaking grates. The grate surface in such 
a case will range between 1 to 35 and 1 to 50. 

Cleaning Fires 

CLEANING a fire is made necessary by the accumulation of clinker and ash. 
which impede the air for combustion. The intervals between cleaning 
depend upon the proportion of ash in the coal and its fusibility, and upon 
the type of grate. If the coal contains much ash, or ash that is fusible, 
the fires must be cleaned frequently. Less clinker forms with light fires, 
which can often be run through a 12-hour shift without cleaning. Fires 
should be cleaned thoroughly, all clinker and ash being removed so that they 
cannot fuse and adhere to the side and bridge walls. Accumulations of 
clinker melted onto the furnace walls reduce the grate area ; and the brick- 
work is damaged when they are eventually broken ofif. 

The more quickly fires are cleaned, the less coal is wasted. The damper 
should be partly closed while it is being done. 

There are two general methods of cleaning fires, the side and the front 
to rear methods. 

In the side method, one side of the fire is cleaned at a time. The good 
coal on the top of the fuel bed is scraped and pushed to one side, large 
clinkers are broken up with a slice bar, and the refuse drawn out of the 
furnace. After one side is cleaned, all the burning coal from the other 
side is moved back and spread evenly over the cleaned part of the grate, 
after which a few shovels of green coal are added. This adding of fresh 
coal is necessary in order to have enough live coal to cover all the grate 
when the cleaning is completed. The refuse is then removed from the other 
half of the grate and the burning coal spread over the whole grate. 

In the front to rear method, the burning coal is pushed back with a hoe 
against the bridge wall and the exposed clinker removed. The burning 
coal is then pulled forward and formed into a narrow ridge across the 
bare grate. The clinker from the back of the fire is ''jumped" across the 
ridge with the hoe, and pulled out through the fire door. The ridge of live 
coal is then spread evenly over the grate. With this method it is difficult 
to get a really clean fire without wasting a lot of unburned coal. 

An improvemeiit on the front to rear method is to form the front of 
the bridge wall into a shelf or cleaning table. The live coal is pushed onto 
the cleaning table, giving every facility for thorough cleaning without waste 
of unburned coal. After the ash and clinker have been removed, the live 
coal is drawn forward from the cleaning table and spread over the grate. 

The height of the cleaning table above the grate should be such that 
it is about level with the top of the layer of ash. This will naturally vary 
with the quality of coal and with the length of time between cleanings, but 
about 6 in. will meet general conditions. 



568 OPERATION 



With anthracite, dumping grates are frequently used. The tire is burned 
very low on one section by not feeding coal to it. and that section is then 
dumped. Burning fuel is pushed onto the clean grate and fresh fuel added. 
Other sections are similarly treated until the whole tire is cleaned. 

Stand-by Boilers and Banked Fires 

TDOWER plants which operate under changeable load conditions must always 
-*- be ready to carry the maximum or peak load, and in order to meet these 
sudden demands, steam pressure must be maintained on the boilers held in 
reserve. 

The length of time that stand-by boilers are held in reserve depends 
entirely upon the service. Boilers are held in reserve in public utility plants 
to meet the peak load demands of morning and evening rush hours which 
come on at detinite times ; and are also held for long periods to meet un- 
expected demands, such as are due to thunderstorms, tire protection serv- 
ice, etc. 

The quantity of fuel used in banking tires does not contribute directly to 
the power output of a station, but rather represents the losses due to radia- 
tion, leakage, etc., called the stand-by losses. Stand-by losses var>- widely in 
different plants and under different operating conditions, as is indicated in 
Table 90 which shows the fuel required for banking tires. 

Table 90. Fuel Consumed by Banked Fires. 

T f 1.1 . Method of Kind of Rated V^^^ ri?%o. 

lype oi Plant t:- - /- i tj xr t^ of Bank, Coal fer 

■'*' I Finng Coal B.H.P. ^^ ^ 



Public Utility | Chain Grate Stoker 111. Bituminous 508 

Public Utility [Chain Grate Stoker 111. Bituminous 508 

Public Utilitv! Underfeed Stoker .Bituminous 600 



2 130 

24 450 

24 ^ 330 



Industrial Hand Fired |\V. Va. Bituminou. 640 72 192 

Industrial Hand Fired IXo. 3 Anthracite 600 24 200 

Industrial Side Feed Stoker 'ill. Bituminous 400 8 260 



It is obvious that the coal required per hour for a short bank will not 
be as high as that required for a long bank, due to the fact that the setting 
remains hot from the previous operating period. 

When burning oil, about 2 per cent of the fuel used when operating the 
boiler at rating, will maintain the full steam pressure for a long banking 
period. 

Quick Steaming From Banked Fires 

Ti OILERS which may be called upon to carry sudden heavy loads must 
^ have free and detinite circulation, as the water must get in motion 
quickly. Boiler circulation is not positive, but is induced by "bubble pump" 
action, w^herein the upward travel of the steam bubbles due to their buoyancy, 
sets the water in motion in the same direction. The unrestricted water passage 
offered by the spacious Heine waterleg is particularly favorable to starting 
circulation quickly. 

The curve of Fig. 243 by G. H. Perkins, of a quick steaming test on a 
950 H.P. Heine boiler, demonstrates rapid response to sudden heavy loads 
by attaining 300 per cent of rating in 4 minutes and 23 seconds, or 3000 H.P. 
in 5 minutes, from a banked tire. 

Forced draft fires, oil or powdered coal, can handle these unexpected 
loads more rapidly than natural draft. The curve in Fig. 243 is of a trial 
with a Sanford Riley Underfeed Forced Draft Stoker. 



OPERATION 



569 



950 
































































































































































































































■ 
















































. 
























300 


























































«-^ 


































































> 






































































y 






































































• 


y 






































































y 
































250 








































/ 






































































/ 






































































y 


/ 






































^ 
































y 


/ 








































$ 






























/ 












































<3'200 




























/ 






































































/ 
















































^ 
























/ 


















































1 

v 






















y 






































































y 


r 




















































"^ 150 


















t 


/ 






































































/ 
























^ 
































k 
















/ 


























































«t 














J 










































































f 




























































100 












/ 






































































J 










































































/ 








































































J 










































































f 


































































50 






J 








































































r 








































































/ 










































































f 








































































/ 











































































/ 




















V 





















































Time, Minutes 

Fig. 243. * Quick Steaming from Banked Fires. 



3850 



2375 



900 



U35 



950 



475 



Load Signals 

TT is often convenient for the firemen to know what load is being carried 
-■' in the engine room, especially in stations where the load is variable. This 
may be readily accomplished by the use of a simple signal system. A box 
with three rows of numbers painted on its glass front, each row from to 9 
with a small lamp back of each number, may be placed prominently in the 
boiler room. The upper row of figures will represent the load in tens of 
thousands of kilowatts, the middle row thousands, and the lower row hun- 
dreds. A bank of twenty-nine switches, each switch corresponding to a num- 
ber on the signal box in the boiler room, will be placed in the engine room. 
The lamps in the signal box will light and inform the boiler room operators 
of the load being carried, as the switches are turned on. 

In very long boiler rooms the signal may be composed of a number of 
lamps arranged as in outdoor electric signs. 

Quite elaborate systems of load dispatching have been worked out in 
large inter-connected power stations. 

Prevention of Smoke 

SMOKE consists of small particles of unconsumed carbon which give to 
the gases a color ranging from light grey to dense black. It is caused by 
the lack of sufficient air at the proper temperature at the point where 
the volatile gases from the coal should be burned, with the result that the 
gases are only partly burned and carbon is set free. 




United Gas Improvement Company's Building, Philadelphia, Pa., equipped with Hein 
Standard BoUers. This company has installed 6200 H. P. of Heine Standard Boilers 



Operation 571 

The density of smoke may be measured in several ways and the most 
popular method is by means of the Ringelmann charts, which are described 
in Chapter 15 on BOILER TESTING. 

Many cities enforce ordinances providing penalties to be inflicted upon 
those plants which are consistent smoke producers. Hence it is the engineer's 
concern to know of the possible methods for eliminating smoke. 

Smoke may be caused by (1) character of fuel, (2) improper method 
of firing, (3) poor furnace design, (4) lack of sufficient draft, and (5) 
insufficient furnace capacity. 

In general it may be stated that bituminous coals of high volatile content 
are more difficult to burn smokelessly than those of a low volatile content. 

When the various methods of firing were discussed earlier in this chap- 
ter, it was mentioned that the particular method selected would depend upon 
the type of fuel. In general, smokeless combustion will be more completely 
attained by firing the coal in small quantities and at frequent intervals. It is 
due principally to this fact that mechanical stokers usually accomplish smoke- 
less combustion. 

Much depends upon proper furnace design. The problem of attaining 
efficient and smokeless combustion resolves itself into three requirements, 
viz. : the mixing of the unburned gases with the proper amount of air for 
combustion, the allowance of time for combustion, and the maintenance of 
high furnace temperatures, all of which depend upon correct furnace design. 

The converse of proper mixing is stratification or laneing, which occurs 
commonly in hand-fired furnaces, and is the more objectionable where the 
gases rise directly from the fuel bed into the tubes as in the case of vertically 
baffled boilers. The installation of wingwalls, mixing" piers, arches, and 
steam jets is often necessary to effect smokeless combustion. But it is diffi- 
cult to construct such arches and piers to stand up satisfactorily under the 
intense furnace heat, and some of these mixing devices take up room, 
diminish the combustion space in the furnace and also reduce the available 
draft. 

The preferable way to reduce smoke and still obtain the proper mixing 
effect in the furnace is to employ horizontal baffles, with a curtain wall added 
for high volatile coals. Fig. 20 on page 93 shows such an arrangement 
which is highly successful. 

Time is also an important element in smokeless combustion and depends 
upon the length of gas travel and the volume of the combustion chamber. 
Horizontal baffling meets this requirement, as has been shown in experiments 
by the- U. S. Bureau of Mines with a Heine boiler in which, with a combustion 
rate of 64.5 lbs. of coal per square foot of grate area per hour, only 1 per 
cent of the total unconsumed combustible was present when the products of 
combustion had traversed 160 cubic feet of combustion space. 

The higher the furnace temperature the more rapid and complete is the 
combustion with absence of smoke, as is shown by tests made on a Heine 
boiler at the University of Illinois. This boiler was equipped with a bottom 
horizontal baffle of C tile which completely encircled the tubes of the lower 
row over the furnace. It was "almost impossible to make smoke with this 
setting under any condition of operation." 

Inasmuch as part of the air for the complete combustion of bituminous 
coal must be drawn through the fuel bed and the rest admitted above the 
fire, it is obvious that smoke will result if there is a lack of sufficient draft. 
The largest quantity of secondary air is required just after firing, and much 
less is needed for the rest of the cycle until the next firing. 

A well designed and operated furnace will burn a given fuel without 
smoke up to a certain critical combustion rate. Beyond this rate the eft'iciency 
will decrease and smoke will result, owing to the lack of air and of furnace 



572 OPERATION 



capacity in which to mix the gases. This is the reason why hand-fired 
furnaces usually smoke when they are being forced to carr}- much overload. 
When fires are being kindled or when banked fires are being forced, 
smoke is almost unavoidable, and most cit>' ordinances provide exceptions 
to their rules to cover these circumstances. 

Cinders. In large central stations operating boilers at high ratings with 
stokers and forced and induced draft, there is often a nuisance caused by 
cinders discharged from the stacks. Attempts have been made to reduce 
this by installing cinder catchers in the stack, but these have not been par- 
ticularlj^ effective. A cinder-separating induced draft fan which is claimed to 
be successful, has recently been placed on the market. 

Meaning of Carbon Dioxide 

THE proportion of CO2 in fine gas is a gage of the success realized in pre- 
venting inleakage, and in securing combustion of the fuel with the minimum 
amount of air. The more nearly the maximum value is approached, the 
greater the success in keeping down the excess air and the consequent heat 
losses up the chimney. This maximum value runs from about 18.5 with high 
volatile bituminous coals to about 20.0 with anthracite. Assuming an all- 
carbon fuel, the percentage of excess air used can be calculated directly from 
the CO2 percentage, and equals : 

m '^-JL (70) 

in which D is the percentage of CO2 by volume in the exit fine gases. As 
each volume of CO2 present is produced by the consumption of an equal 
volume of cxy-gen, the numerator in the fraction represents the unconsumed 
or excess oxj-gen remaining in the gas. and the denominator the oxygen 
actually consumed; that is, the amount theoretically required for combustion. 

Fig. 244 indicates the amount of excess air, and the preventable fuel 
loss corresponding to obsers'ed percentages of CO2 based upon average coals. 
Good practice is represented by 15 per cent CO2, which corresponds to 40 
per cent excess air, with practically no preventable loss up the stack. In 
the absence of effort to maintain high values of CO2, a usual average in 
a great man}' power plants is as low as 5 per cent. 

Of course, the exact amount of excess air and the preventable fuel loss 
will depend upon several circumstances. The chart, Fig. 245. by Haylctt 
O'Xeill, shows the effect of the flue gas temperature on the efficiency with 
different proportions of C0». These curves are topical, although they were 
drawn for the following specific conditions : 

Coal. B. t. u. per lb 14.500 

Comxbustible. per cent — 90 

Volatile hydrogen, per cent 5 

Moisture, per cent 2 

Relative humidity of air, per cent 65 

Temperature of air, deg 80 

CO in flue gases, per cent 0.1 

Steam pressure, lb. per sq. in 150 

Combustible in ash, per cent. —.. 30 

The overall efficiency decreases as the CO2 content is reduced, and as 
the exit temperatures are increased, except with low flue temperatures. These 
correspond to lov/ rates of driving, with high radiation losses and low 
efficiency. 



OPERATION 



573 





700 

600 

cSOO 
o 

;>• 

I4OO 

C 
< 

w 

S300 

200 

100 












■ 






















^ 
















































(is-l 
























































































































60- 
















































































55- 




















































































' 


































50- 














































































-»- 






I 


































«45- 






\ 


































u 






I 


































^ 






\ 


































in 40- 






\ 


































o 
_1 






' 


































JZ5- 














































































t) 








\ 
































-^30- 








\ 






































\ 
































c 








\ 
































^25- 








\ 


i 








































\ 








































\ 






























IQ^ 










\ 


\ 








































\ 




























15- 












\ 








































\ 








































\ 


























10- 
















\ 








































\ 


\ 








































\ 


s. 




















S- 




















V 


S, 








































^ 


\ 










































"^ 


*>s 












































^^ 








« 






































^. 



6 8 10 12 14 
Carbon Dioxide, Percent 



18 20 



Fig. 244. Chart for Estimating Excess Air from 
Per cent of Carbon Dioxide. 



A high value of CO2 Is constantly sought in boiler operation. Few 
boilers are operated with an air supply even approaching the minimum, and 
the amount of CO in the flue gas becomes objectionable only when the air is 
so reduced that the CO2 is above 15 per cent. The CO2 is generally low when 
surplus air is introduced, and is increased by adjusting the draft and fuel-bed 
resistance, by closing holes in the setting, and by avoiding holes in the 
fire. With complete CO2 records the work of different firemen can be 
checked. When these records cannot be kept, special tests can be made 
and the conditions under which they were produced studied, so as to fix 
a standard of operation. Samples of such studies are given in Fig. 246. 
A comparison, of samples from different passes indicates leakage through 
the setting. 



574 



OPERATION 




"400 500 &:o ::o boo 900 1000 1100 

Flue Gas Temperature, Deg. F. 
Fig. 245. Boiler Efficiency as affected by Flue-Gas Temperatures. 



Effects of Firing on Carbon Dioxide 

A COMPARISON of firing conditions with CO, records, either from an 
'^*- automatic chart or from one made bj- plotting the analysis of grab 
samples against time, indicates the effect of different operations on furnace 
efficiency. Fig. 246 illustrates the method. 

In A. which is hand-firing, the fire was dirt\- and the COj was down to 
5 per cent ; but after cleaning, it rose to 13 per cent. 

Record B was made with a sloping grate stoker, and shows how the 
CO2 fell as the fire was cleaned, and rose as soon as the dump grate was 
closed. It was customary- to poke coal down from the hopper soon after 
each cleaning, and this was accompanied by a big drop in CO;, which indicated 
the entrance of much excess air due to the upper part of the grate being cov- 
ered with unignited coal. As this new coal became ignited, the COi again 
rose. 

The latter part of C shows good hand-firing; the COi rises after each 
firing and falls slowly. The first firing was uneven, and quickly burned into 
holes, which reduced the COj to 3 per cent. 

The effect of leveling a fire which was full of holes is shown in D. 



OPERATION 



575 



20 
18 

O 6 



20 

18 

J 6 

Oh 

U 8 
6 



n 
























1 
















c 

p 

c 
«3 








1 








^>1 


i 


















































^ 


































/ 




























( 














- 














1 






















'^ 




^ 




1 




























S, 


/ 

















































V 



I ? 5 4 5 6 7 6 9 10 11 I? 15 14 15 16 
Time in Minutes 

■Dirty vs. clean fire, hand firing 



















































































/— 











/— 






/ 


^N, 






/ 






•>> 




/ 


'\ 


^ 


/ 


N 


\, 




/ 






"s 


sy 








/ 




\, 




















/ 




N 


. / 










.5; 















'^g. 














L 


l.. 















5 10 



15 20 25 30 35 40 45 


50 


55 60 


Time m Minu+es 




PoJ-.^ 



C — Good band firing 



I 3 

I 2 

~1 1 
o 
OlO 





1 




/-^ 




i 

1 

§ 
<- 








<— ' 


— 1 














\ 






/ 














\ 




/ 










/ 






\ 














/ 






\ 


/ 




















/ 
















/ 










/ 














> 


/ 










y 














I 














































L 









12 3 4 5 
Time in Mmu+es 

B — Sloping grate stoker 





1 ■ ■ 




■ k- ' ■ ' ' 












r 








V 






















"V 


N, 
























N, 




J 






1 




















[-~^ 


^1 
•^1 






































I 

1 





















J 2 



3 4 5-678 
Time in Minutes 



9 10 It \12 



D — Effect of leveling fire 



Fig. 246. Variation of CO2 with Different^Methods of Firing. 



Fig. 247, by M. GenscJi, shows the general effect of excess air. The 
fuels for which results were plotted are typical high-grade and low-grade 
coals, so that values for other coals would lie in the bands between the 
different pairs of curves. The combustion temperature and the efficiency 

100 



90 £ 
u 

80 1 





































4500 


^ 
































"^ 


I- 




•^ 




1 




















4000 


V 


\ 




>«. 


■«. 




f^ 


C-/6 


A>. 
















\ 




\ 






v, 


■>«. 


'^ 


S^ 


^ 














o3500 




\ 




\^ 


h 








«» 


. 


*V 


"«s 














\ 


\ 


\ 










"^ 


'^K 


^ 


^ 




^ 


£^•3000 








\ 


s 


[<: 


c^ 












"^ 


s. 


•^ 










> 


V 


N 


&^ 














/ 


/< 


D2500 

+- 














V 


s 


^ 


h 










/ 
/ 


/ 


















' N 


s 


h' 




y 






i_ 




■Coal No. 1 






^, 


^y-. 


> 


y 








g.2000 




Loa/ no. / 


t 


. 


> 


/ 


"-^ 


-^ 


^^ 




,^ 


1-1500 
















A 


/> 


> 










^ «, 


•■^ 










d 


0', 


y 


k^ 
















1000 








fw;^ 


u 


y 
























^ 


.^ 
^ 


^ 
f 


' 1 1 1 1 
-i.ip <^ni<; Temper 


afure^ 






Rno 


^ 


^ 


^ 




/ 




j=j 


=- 


"T 


"-■ 




•■" 










— 


— 




























n 



































3000 
2500 
2000 
1500 
1000 



^60^ 



50 



<j) 



o 

500 ^ 

u. 



50 100 150 

Excess Air. Per Cent 



200 



Fig. 247. 



Effect of Excess Air on the Combustion of High-Grade and 
Low- Grade Coals. 




A part of the 2844 H. P. installation of Heine Standard Boilers in the United State 
Government Hospital for the Insane, Anacosta, D. C. 



OPERATION 577 



fall as the amount of air increases. At the same time the flue gas volume 
increases, resulting in greater load on the draft fan and on the chimney. 

The admission of undue excess air through the fire bed is corrected 
by adopting standard methods of firing. Air leakage through the setting 
can be eliminated only by testing every point where air might possibly get 
in and by stopping up the cracks. The flame of a lighted candle held next 
to the cracks will indicate whether any air is being drawn in, or the sudden 
closing of the damper when the fire is operating at a high rate will cause 
smoke to issue from the cracks. 

Cracks can be caulked with a mixture of fire-clay and waste, or with 
magnesia covering made into a paste. Several coats of asphaltum-base paint 
should be applied to leaking settings. 



Carbon Monoxide 

I "HE presence of CO or carbon monoxide in flue gas indicates partly- 
-*■ burned carbon ; the cause may be insufficient air, poor mixing of the air 
with the combustible gas, reduced furnace temperature, or the rapid distilla- 
tion of volatile after firing, with insufficient secondary air to consume it. 
The CO may be present even with high O2, as when the fire is clogged at 
some points and air is coming through large holes at others. 

Any CO produced in a furnace results in the loss of 70 per cent of the 
heat of the carbon involved, and furthermore the presence of CO indicates 
that other comlnistible gases such as hydrogen and hydrocarbons, are 
escaping unconsumed. 

Carbon Dioxide Recorders 

'~r'HE maCthod of analyzing flue gas by means of the Orsat apparatus is 
J- described on page 532. While hand indicators, such as the Orsat, can 
be used as a means of studying air-supply conditions, or for occasional tests, 
as discussed on page 574, they do not answer the purposes of daily plant 
operation, since the CO2 content of the flue gases varies widely, due to the 
fact that the proportions of air supply through and above the fire are easily 
unbalanced by the firing of fresh coal, open fire doors, holes in the fire, 
damper manipulation, etc. Hence a number of instruments have been de- 
veloped that will test automatically the quality of the flue gases and make 
a continuous graphic record of the percentages of CO2 they contain. These 
furnish a definite and permanent record, which assists not only in correcting 
improper combustion, but also has a moral effect in maintaining the right 
conditions. 

The recording instruments depend for their operation upon the absorp- 
tion of CO2 from a sample of the flue gas, usually by means of a solution 
of caustic potash, though sometimes it is used in the solid form. In one 
instrument it is replaced by ordinary quick lime which has similar absorbent 
properties. 

Several different methods are used to measure the sample of gas, and 
to bring it into contact with the absorbent. In one type of instrument a 
flow of water trickles continuously into' a container. When this container 
becomes full, it is suddenly emptied by a siphon action which draws in a 
measured sample of the flue gas. This is then put into communication with 
the chamber containing the caustic solution. The diminution of its volume 
by the absorption of the CO2 is measured by the descent of a gas holder in 
which it is contained. The motion of this holder causes a pen to draw a 
line on a chart, the length of the line being proportioned to the CO2 percent- 
age. This cycle of operation takes place every few minutes, according to 
the rate of flow of the water. 



578 O P I£ R A T I O X 



In another tj-pe of instniment the reduction of pressure caused by the 
absorption of COa is used to indicate the percentage. By means of a steam 
jet aspirator, a small current of flue gas is drawn continuously through a 
chamber containing the absorbent. When the CO* is eliminated, the pressure 
in the chamber is reduced, and the reduction is measured by a manometer or 
other form of pressure gage. This method pro\"ides a continuous record, 
and the recording instrument can be placed at a distance from the boiler 
room. In an alternative plan, flue gases are drawn through a chamber in 
which the absorbent is covered by a porous pot The reduction of pressure 
inside this pot is utilized to operate the manometer. In both these types, 
however, more absorbent is consumed than in an intermittent test, and the 
steam used by the jet may be considered as wasted. 

In a third method of determining CO*, the flue gases pass through two 
ordinary- gas meters, one before absorption and one after. The second one 
will work more slowh*, as it naturally has less gas to measure. The differ- 
ence in their speed is recorded by a differential gear, which operates the 
pen producing the record. In this type of instrument, dry calcium hydrate 
forms the absorbent, and the gases are drawn through the meter b}- a 
water jet. 

A CO3 recorder should run indefinitely, and the onl\- attention required 
should be to change the chart, renew chemicals, and change the filtering ma- 
terial in the gas line. The instrument should compensate automatically for 
temperature changes, changes of volume and specific gravity in absorbent 
solution, and changes of draft in boiler. It should have a minimum number 
of moving reciprocating parts. It is desirable to have a recorder for each 
boiler, but if one recorder is used for a battery of boilers, the piping should 
be arranged so that the firemen wiU not know which boiler is connected. 
This can be accomplished by running the gas pipe from the boiler to a 
coramon header, and then boxing the valves on the header. 

A CO2 recorder made by the Mono Corporation of America, is shown 
in Fig. 248, which may be operated with either water or compressed air at 
a minimum pressure of 8 lbs. The manufacturers state that it will make 
records of up to 40 analyses per hour. The pressure medium, by which the 
apparatus is driven, passes through a regulating valve and the receiver into 
a bottle containing mercury. This forces the mercurj- from the bottle up 
through a system of tubes, of which one leads to the volumeter and another 
to the gas release outlet. When all the mercuni- is thus displaced, the pres- 
sure in the bottle is released through contact with the atmosphere. Then 
the mercury, which was forced up the tubes, recedes to the bottle, sealing the 
receiver, and the C3'cle is repeated. In this way an alternating rising and 
falling movement is employed in drawing in the flue gas for anaUsis and 
letting off excess gas. 

As the mercury falls in the volumeter, the gas to be analyzed is drawn 
in through the gas inlet and mercurj- seal. When the mercury rises, the 
gas in the volumeter, which contains ICO cc, is forced through the tubes and 
a second mercury- seal to the caustic potash container, which is filled with the 
absorption liquid and through which the gas bubbles, thus making the 
absorption of COa complete. The remainder of the gas passes into the 
gasometer, which is suspended in a glycerine solution, where it is measured 
again at the same temperature as in the volumeter. As the gas enters, the 
gasometer rises, turning the pulleys from which the recording pen is sus- 
pended- When the pen has come to a stop on the chart, the mark indicates 
the percentage of gas absorbed. Then the gas in the gasometer is released to 
the atmosphere, and the apparatus is ready for a new anahsis. 

The COs record furnishes a good index of furnace performance, but a 
knowledge of the percentage of CO in the escaping flue gases is also ^-aluable. 
Records of CO can be secured from an instrument consisting of a Mono COj 
recorder and a special CO attachment. The CO* recorder is of the usual ab- 



OPERAT ION 



579 




Caustic Potash 
Container 



Fig. 248. Mono CO2 Recorder. 

sorption type, operated either by air or water pressure. When CO is to be 
measured, a chamber containing an electric furnace and the chemicals to 
carry on the reactions is mounted on the wall next to the recorder. Either 
CO or CO2 can be shown on the chart, but the two cannot be recorded simul- 
taneously. The usual practice is to supply CO2 instruments for each boiler 
and one complete CO recorder, arranged to be connected to any unit, for 
each plant. 

Draft Instruments 

'T~'HE difference of pressure causing the flow of gases through fuel bed 
-L and boiler is referred to as "draft," although the term is sometimes 
loosely applied to the motion of the gases. These pressures are measured 
by instruments called draft gages, and are usually expressed in inches of 
water. 

Draft gages may be simply glass tubes bent into U form and half 
filled with water. The differences in level are frequently so small that they 
are difficult to read accurately. The bore of the tube should be the same 
in both legs, or error is introduced as may be seen by the liquid standing 
at different levels in the two legs when both are open to the atmosphere. If 



5S0 OPERATION 



the inside of the tubes is not clean and free from grease when water is used, 
the water will not freelj- ""wet" the glass, and the surfaces in the two legs 
will not be similar in height or shape when the gage is "free/' Readings 
should be taken from the lowest part of the meniscus with liquids which 
wet the glass, such as water ; and from the highest part of the meniscus with 
liquids which do not wet the glass, such as mercury. 

When the pressure fluctuates so rapidly as to interfere with observation, 
the pulsations may be damped in a plain U-gage by putting a few small 
stones or some sand in the lowest part of the tube. 

To facilitate reading the gage when the differences in level are small. 
verniers are sometimes provided. 

Various devices are used to exaggerate small pressure differences. th:v.gh 
some are delicate and only suitable for laboratory- work. In gages for the 
boiler room, flexible diaphragms, slanting tubes, and non-miscible liquids 
in combination with small bore tubes connecting the U-gage legs, are used. 
In the slanting tube gages, mineral oil of a sp.gr. less than unit\- is generally 
used; and it is highly colored, bright red or blue, so that the instrument can 
be easily read. 

A simple draft gage indicates the difference in pressure between the 
point to which it is connected and the atmosphere, while a differential gage 
indicates the difference in pressure between two points in the gas passages. 
Fig. 249 illustrates a Hays differential draft srase. 




Fig. 249. Dinerential Draft Gage made by 
Jos. W. Hays Corporation. 

Compound and triple types of differential gages are composed of two 
and three single instnmients respectively. With these, the draft can be read 
simultaneously at different points in the setting. For forced or balanced 
draft, the scale of a single instrument can be divided with the zero point 
about midway. The liquid then moves to the right under a vacuum and to 
the left under a positive pressure. 

The gage should be located so that it can be seen by the fireman when 
he is setting the damper. The connections from the gage are usually of 
%-m. pipe, this being led through a larger pipe into the furnace, pass or 
flue. The connection should merely project through the wall, to prevent 
the burning off of the end. The piping into the furnace should be as 
close as possible to the front and to the top of the chamber, to avoid slag 
accumulation. 

An indicating instrument of the diaphragm type. Fig. 250, is used for 
forced draft installations. This has three scales, reading from to 2 in. of 
water for the flue connection, 1-in. vacuum to 1-in. pressure for the com- 



OPERATION 



581 



bustion chamber, and to 6 in. pressure for the ash pit. The varying pres- 
sures are transmitted by diaphragms to plungers, which are attached to 
horizontal shafts by links or levers. The indicating pointers are carried on 
these horizontal shafts. 





Fig. 250. Triple Draft Gage made by 
Precision Instrument Co. 



The Significance of Draft. Efficient combustion requires that a certain 
quantity of air be supplied for each pound of fuel burned. Therefore, the 
quantity of gases passing through the boiler setting will be almost in direct 
proportion to the load on the boiler when combustion is progressing properly. 
And inasmuch as the boiler heating surface interposes a resistance to the 
flow of gases, a differential draft gage indicating the pressure drop or draft 
loss between furnace and up-take, will act as a gas fiow meter and indicate 
whether or not the proper quantity of air is being supplied for the given load. 
A differential gage so located will also indicate the cleanliness of the gas 
passages, since an undue increase in draft loss will mean that they are be- 
coming clogged. 

A differential draft gage connected so as to show the draft loss through 
the fuel bed, in conjunction with one showing the drop through the boiler, 
will indicate any change in the furnace conditions. A relative increase 
in the fuel bed drop will indicate that the fire is becoming thicker, or that 
it is becoming clogged with clinkers and ash. Similarly, if the pressure drop 
becomes less, it indicates that there are holes in the fire or that the fuel bed 
is too thin. The above principles are made use of in so-called combustion 
meters and efficiency indicators in which fixed points are set by test on the 
gage scale representing the best draft relations for the particular unit. 
Deviation from these points warns the operator of unfavorable conditions. 




Union Trust Building, Cincinnati, Ohio, equipped with Heine Standard Boilers. 



583 




B/o^ Off 
Fig. 251. Mason Damper Regulator. 



584 OPERATION 



Draft Regulation. Combustion can be controlled automatically by vary- 
ing the supply of air or fuel passed through the boiler furnace. For natural 
draft the control is secured through movements of the breeching or stack 
damper. For forced draft, the supply of air can be varied also by varying 
the fan speed, or by adjusting a damper placed where the air enters the 
furnace. 

The hydraulic damper regulator is used in natural draft plants. As 
shown in Fig. 251, this is operated by the variation of steam pressure in the 
boiler, but water pressure is used as motive power. The change in steam 
pressure moves a lever, which opens a pilot valve controlling the supply 
and discharge of water. The piston contained in the regulator cylinder is 
moved when water is admitted, the damper movement being controlled by 
connections from the piston stem. As the piston moves, it displaces the 
fulcrum of the pilot valve lever and closes the pilot valve. Consequently, the 
piston does not make a full stroke, but graduates the damper opening to 
the load. 

In small forced draft installations, where the stoker and fan are driven 
by the same engine, both fuel and air supply can be controlled by the stand- 
ard hydraulic regulator, according to the variations in steam pressure. In 
larger installations, when separate units drive the fan and stoker, the speed 
of the former can be controlled b}- a balanced valve on the steam line. The 
speed of the stoker engine can be controlled by the pressure in the wind-box. 

When variable speed motors are used for the stoker or fan drive, they 
can be controlled automatically by rheostats operated from the hydraulic 
regulator. 

In so called "balanced draft" systems it is the aim to keep the furnace 
chamber automatically at atmospheric pressure, and this is usually accom- 
plished by means of a regulator with a relay which controls two hydraulic 
cylinders, one operating the air supply damper and the other the stack damper. 

Economical Operation 

"Vy/lTHOUT suitable instruments and organization, it is impossible to tell 
^^ whether the boiler efficienc}' is 50 or 75 per cent, or why it is so. 
Unless the management knows what should be done, it cannot reasonably 
complain that the boiler room force does not do it. The operation of gener- 
ating steam should be investigated and controlled by intelligent planning, 
as much as is the case with other manufacturing operations. 

Control Boards. The necessity of installing instruments for controlling 
combustion and boiler operation is gaining recognition and many modern 
plants have these assembled on an instrument or control board. These boards 
may be of two general types, the one containing instruments which serve a 
whole boiler room and the other containing instruments which serve only 
one individual boiler or battery. In small plants the first tj-pe is satis- 
factory-, but in large plants the individual control board is to be preferred. 

Such boards carry indicating and recording steam flow meters, recording 
pressure gage, recording thermometers for feed water, superheated steam, exit 
gases from boiler and from economizer, direct and differential draft gages 
with selecting valves, stoker and fan speed controls ; and CO^ recorders and in- 
dicating and recording water meters are nearby. The design and equipment of 
these boards is entirely dependent upon the particular conditions to be met. 

A desk and chair should be provided for convenience in keeping a log, 
and in calculating, tabulating and comparing data. 

Fig. 252 illustrates an instrument and control board with Venturi indi- 
cating, recording and integrating meter conveniently near. 



OPERATION 



585 



Eificimt Operation. With an installation of this kind, used with reason- 
able intelligence and enthusiasm, there is no reason why the boiler plant 
should not be run continuously under "test conditions." 




Fig. 252. Instrument and Control Board by W. N Polakov and Co. 



The control board shown in Fig. 252, combined with a course of training 
and assisting" the boiler room force, and a system of secondary payment 
for actual economy effected, resulted in the following drop in cost of gener- 
ating steam while the cost of coal rose 30 per cent and of labor nearly 50 
per cent. The figures of Table 91 were supplied by W. N. Polakov as 
representative of a number of plants whose operation has been similarly 
improved. 




X 



3 



c 

Q 



O 

O 



'Jl 



OPERATION 



587 



Table 91. Reducing Cost of Generating Steam. 



Moi?h Total Cost 


Total Weight of 
Steam Generated 


Cost of 1000 
Lbs. of Steam 


January 

February 

March 


$24,086.27 
22,345.38 
21,895.90 


25,381,000 
23,400.000 
24,571,000 


$0,951 
.953 
.693 


April 

May 

June 


18,985.05 
16,340.47 
18,142.36 


29,741,066 
26,900.000 
26,476,000 


.637 

.572 
.685 


July 

August 

September 


16,987.25 
18,983.40 
16,384.33 


36,127,000 
36,166,000 
33,527,000 


.468 
.525 
.488 



Measuring Water 

rHE principal methods used for measuring water are given in outline form 
*■ in the following table : 





Table 92. Methods of Measuring Water. 


General Method Examples 




Gravimetric or Actual Weighing Tanks and Scales 

Tilting Weighers 



Volumetric Displacement 



Tanks 

Tank Meter 
Piston Type Meter 
Rotary Type Meter 
Disk Type Meter 



Weirs 



V-Notch 
Cycloidal 
Trapezoidal 



Velocity of Flow 



Venturi Tube 
Orifice 
Pitot Tube 
Pitometer 



The volumetric and gravimetric methods are accurate and useful when 
the flow does not need to be continuous. When the liquid must flow in a 
continuous stream, the pitot tube, orifice, venturi tube, or weir methods must 
be employed. The first three of these can be conveniently and quickly applied 
for measuring liquids flowing in closed pipes under pressure. In these three 
methods, however, the pressure is the factor actually measured, and it varies 
as the square of the rate of flow. Accuracy is secured therefore only for 
flows between the maximum for which the instrument is designed and say 
Vs or J^ of this maximum. At smaller flows the head is extremely small, 
and any friction in the moving parts of the instrument introduces a serious 
error. 



OPERATION 




Fig. 253, Worthington Water Weigher. 




Fig. 254. Hammond Volumetric Meter. 



OPERATION 



589 



The plain orifice, either submerged or discharging into free air, presents 
the same difficulty at small heads. The ordinary rectangular weir is better, 
but each size of weir requires a different device for converting head to flow 
in a recording and integrating instrument. In the V-notch or triangular 
weir, the cross-section of the issuing stream is a similar figure at all heads, 
so that the relation of flow to head is fairly constant. 

Gravimetric meters depend upon the actual weighing of the water. Two 
tanks are arranged so that they can be filled until a definite weight is balanced. 
They are then dumped alternately, a record being made of the number of 
dumpings. This same method is used in testing work, except that the tanks 
used rest upon platform scales. Fig. 253 shows a gravimetric meter. 




Fig. 255. Valve Gear of Hammond Volumetric Meter. 



The Hammond volumetric meter, made by the Alberger Pump and Con- 
denser Co., is illustrated in Fig. 254 and 255. Two chambers are alternately 
filled and emptied, and the cycle recorded on a counter. The valve gear is 
operated by the pressure exerted on the discharge valves and timed by the 
movement of the floats ; and it swings the guide which directs the water into 
cither of the compartments. The valve gear is shown in Fig. 255. An 
outstanding feature is the ease with which the vital parts can be seen and 
the accuracy of operation checked. For instance, a needle gage is provided 
for each compartment, and this may be observed at any time to see that the 
gear trips exactly at the right level. The error between zero and maximum 
rated capacity is guaranteed to be within ^ of 1 per cent. 

In a V-notch meter designed primarily for use with open feed-water heat- 
ers (see Fig. 168, page 325), a float operates the recording and integrating 
mechanism. The motion of the float is communicated to a cylindrical drum, 
which is attached to a disk provided with a spiral slot. This slot forms a 
cam, the motion of which is imparted through a follower to the indicating, 
recording and integrating mechanism. The meter and recorder shown in 
Fig. 168 is accurate to within less than I'/y per cent. 



590 



OPERATION 



'Day Clock in 

Metal Case -- 



Adj'u sling Slop 

4- Day In fegraling 
Clock- 
Aluminum Yoke 

Cam Roller 

Support -for 

IndicaforDial 

Zero Line 

Cam 

Main Shaft 



Main Lever 

from Float 




Metal Disc 

for Chart 

Capillary Pen 



Pen Arm 
■Aluminum Disc 



Counier Dial Plate 
Counter Dial 



Stop 



Indicator Dial 

Hand. 
Indicator Dial 

Removed 



<-— Case 




Fig 256. Venturi Metering Tube and Measuring Mechanism. 



OPERATION 591 

The theoretical discharge over a V-notch weir is given by the formula 

where Q = discharge in cu. ft. per sec. 

H = height of water above bottom of notch 
B = half the breadth of notch at water level 
2 = slope of the notch, or the quotient B/H. 

For a right-angled notch, the slope ^ becomes unity. Combining a co- 
efficient of discharge with the constant part (assuming g to be constant) 
of the above equation, the formula for discharge over a right-angled V-notch 
weir with sharp edges may be written 

Q = CH'^' (72) 

H^ W. King made a thorough investigation at the University of Michi- 
gan, supplemented his results by the experiments of Thompson and Barr, and 
deduced the following expression as the mean of experimental results : 

Q = 2.S2H'-" (73) 

Venturi meters for measuring hot water are generally made in from 2 
to 12-in. sizes. Fig. 256 shows a typical arrangement of meter tube and 
measuring mechanism. The meter actually registers in gallons, but is usually 
calibrated to read in pounds. Table 93 shows the measuring capacities of 
standard meter tubes. For hot water, extra heavy meter tubes with American 
Extra Heavy Standard flange ends are usually selected. The meters are 
graduated for a standard temperature of 62 deg., so that the correction curve 
furnished by the manufacturers must be used for other temperatures. If the 
meter tube is placed in a pipe line subject to pulsations from the pump, an air 
chamber must be installed. 

The formula for measuring the flow of water through a Venturi meter 
(Fig. 256) is 



U= t a ^\ . . . „ (74^ 



(fy- 



where Q := discharge in cu. ft. per sec, 

C = a constant, usually taken as 0.97, but Goodcnough gives 0.98 

for the meters now on the market 
A = area in sq. ft. at entrance to meter (A) 
a = area in sq. ft. at throat (B) 

//= difference in heads at entrance (A) and throat (B), re- 
spectively. 

In the flow meter shown in Fig. 257, either a pitot tube or an oriflce is 
inserted into the pipe where the flow is to be measured. The pressure differ- 
ences created by the flow are transmitted to a murcury column in the meter 
body. The rise and fall of this column are made to engage and disengage 
conductors which vary the electrical current flowing through a circuit. The 
measuring mechanism is included in this circuit. The indicating, integrating 
and recording mechanism really measure electrical quantities, although these 
are proportional to similar quantities (flow, amount, etc.) for the fluid pass- 
ing through the pipe. 




o 



C - 

■!-> Co 

WW 

a; « 

'^ o )r{ 

CO "o 

+j CO "^ 

*-■ CO 
*" C 

■5 gw 
o .^ 



O 4J ^ 

w 5- o 

p O CO 

o g 13 

o ^ r 

4J . o 

Uu ► 

.tfh. t\-i ai 



00 4J "O 

O CO c 
Pli CO 

- 4; O 
<u w u 

^ CO 

O w 

CO 

a 

4-> 
CO 

4J 

C/3 

<u 

•4-1 



OPERATION 



593 





Tabic 


;93. 


Measuring Cap 


acities of Venturi Hot Water Meter 


3. 


Pipe 
Diameter, 


Length of 
Meter 
Tube 

Ft. In. 


Length* 

of 

Inlet 

Pipe, 

Ft. 


Boiler Horsepower 
(301b. per hp. per hr.) 


Water Flow, 
Pounds per Hour 


Water 
Gallons 


Flow, 

per Min. 


Inches 


Minimum 


Maximum 


Minimum 


Maximum 


Minimum Maximum 


2 


1 
1 
1 


11^ 
7 


2 


45 

65 

115 


590 

850 

1,500 


1,360 
1,960 
3,470 


17,600 
25,400 
45,100 


3 

4 
7 


35 

50 
90 


2M 


2 
2 
1 


4^ 
3 


2 


85 
115 
180 


1,150 

1,500 
2,350 


2,660 
3,470 
5,420 


34,500 
45,100 
70,400 


5 

7 
11 


70 

90 

140 


3 


2 
2 

2 


11 

7M 
4M 


2 


115 
180 
260 


1,500 
2,350 
3,380 


3,470 
5,420 
7,820 


45,100 

70,400 

102,000 


7 
11 
16 


90 
140 
205 


4 


4 
3 
3 


3M 
6 


3 


180 
305 
465 


2,350 
4,000 
6,000 


5,420 

9,170 

13,900 


70,400 
119,000 
181,000 


11 
18 
28 


140 
240 
360 


5 


5 

4 
4 


1% 
2 


3 


305 
465 
725 


4,000 
6,000 
9,400 


9,170 
13,900 
21,700 


119,000 
181,000 
282,000 


18 
28 
43 


240 
360 
560 


6 


5 
5 

4 


11 

10 


3 


465 

725 

1,040 


6,000 
9,400 

i3,eoo 


13,900 
21,700 
31,300 


181,000 
282,000 
406,000 


28 
43 
63 


360 
560 

810 


8 


7 
6 
6 


6^ 

IIM 
2 


4 


870 
1,230 
1,850 


11,300 
16,000 
24,100 


26,500 
36,600 
55,600 


344,000 
476,000 
722,000 


53 
73 

111 


680 

950 

1,440 


10 


9 
8 

7 


4% 

7 

6 


5 


1,230 
1,850 
2,900 


16,000 
24,100 
37,600 


36,600 
55,600 
86,900 


476,000 

722,000 

1,129,000 


73 
111 
174 


950 
1,440 
2,260 


12 


11 
9 
8 



11 
10 


() 


1,850 
2,900 
4,200 


54,200 
37,600 
54,200 


55,600 

86,900 

125,000 


722,000 
1,129,000 
1,626,000 


111 
174 
250 


1,440 
2,260 
3,250 



♦This column gives the minimum lengths of straight inlet pipes. Gate valves or other fittings 
to disturb the smooth flow of water should not be inserted in these pipes. 



594 



OPERATION 






"^s 


::i: 




k ^ 


- 






1 

1 
1 

h'tection 
Flow 






"^. 





c5 



\^ - 1 14; - D vnamii 



ic 



AAA 



Terminal ? 



Resisiances--- 

Coniact 

Chamber - . 




l^-S'j"c 



ra.Tibers 



Mercury 
Column.^ 



Fig. 257. Republic Flov.- Meter for Measuring Water or Steam. 



Practically all of the so-called flow meters on the market are applicable 
with certain modifications to either steam or water measurement. Other 
t>-pes of flow meters are described imder "Metering Steam." 



OPERATION 595 



Metering Steam 

\/fOST practical steam meters are based upon one or the other of two 
^^ ^ principles, both depending on the velocity of flow. Either there is a 
constriction inserted in the steam pipe so as to cause a small pressure differ- 
ence, which will vary with the amount of steam passing, or the velocity of 
the flowing steam is measured by a pitot tube, or else the steam in flowing 
through an orifice impinges against a movable part which assumes different 
positions for different rates of flow. 

The actual measuring instrument can be placed at any convenient dis- 
tance from the steam pipe and is connected to it by two small copper tubes 
filled with water of condensation. These tubes transmit the differential pres- 
sure to the instrument. The latter can either indicate on a dial or scale 
the rate of flow of the steam at any instant, or record the rate of flow 
graphically on a chart, or integrate numerically by means of a counting 
mechanism the quantity which has passed in any given time. All these 
functions can be combined in one instrument. 

In instruments using the constricted-pipe principle, the quantity of steam 
passing per unit time is taken as being directly proportional to the square 
root of the difference of pressure on the two sides of the constriction. This 
proportion holds, however, only if the pressure and the superheat of the steam 
are constant. In the simplest form of pitot apparatus, two tubes are inserted 
through the side of the steam pipe, one being cut off flush with the inner 
wall of the pipe and the other bent so that its open end faces the flowing 
steam. Both tubes are submitted to the static pressure of the steam, but 
the bent one measures also the dynamic pressure due to the velocity. The 
difference in pressure in the two tubes is therefore a measure of the rate 
of flow and can be employed to operate an instrument. The disturbance of 
the flow due to the presence of the pitot tube itself must be reckoned with. 

An alternative to the fixed orifice consists of a variable orifice designed 
to create a constant pressure drop. The steam passes upward through the 
seat of an automatically lifting valve, which is held in a higher or lower 
position according to the rate of flow. A lever mechanism connects the 
valve Vv^ith the pointer of the instrument. At low velocities the forces acting 
are so small that the readings are unreliable. In Instruments depending upon 
the drop of pressure across an orifice, this difficulty can be overcome either 
by inserting a smaller orifice, or by using a butterfly valve which can be locked 
in one of several positions according to the rate of flow. Thus the range 
of the Instrument can be altered without Interfering with the steam pipe. In 
every type of instrument referred to, however, accurate metering is difficult 
when the density of the steam varies. 

The best steam meters working under commercial conditions are correct 
within plus or minus 2 per cent at loads ranging from three-quarters to full 
load. At half load the accuracy will be within 2^ per cent, and from one- 
quarter to one-sixth load it will be within 4 per cent. Such accuracy can be 
obtained only by calibrating each instrument under conditions similar to 
those under which it will have to work. 

In the simplest instruments, namely, those that merely Indicate the rate 
of flow at an instant, the dift'erential pressure acts upon liquid in a U-tube, 
the liquid rises in one limb and Indicates by Its height the rate of flow. This 
is read off a graduated scale placed alongside the liquid column. Water is 
sometimes used as the indicating liquid, partly on account of the ease with 
which it is automatically supplied by condensation, and partly because of 
the open scale obtained with small pressures. Mercury, however, is fre- 
quently adopted. 




1.2" 
- R o 



> - o 

u 

t5% 






— — 2. 

- = £ 

— i o 

:: 3". y 



o 
o 
irj 



OPERATION 



597 



The instniinent shown m Fig. 261 uses the orifice principle at a constant 
difference of pressure, the size of orifice being- varied to allow different 
amounts of steam to pass. This is accomplished by a float set in the orifice, 
so shaped that its motion changes the effective area of the orifice. The float 
movement is transmitted to an arm carried by a horizontal shaft projecting 
through the casmg, and carrying, at its outer extremity, the recording pencil 
and indicator pointer. 



Inlet 




Fig. 261. Mechanism of Variable Orifice Type of Steam Flow Meter. 



Some of the instruments used to measure water (see Fig. 257) can also 
be used to measure steam. In the latter service, however, a condenser must 
be used so that the steam does not come directly into contact with the 
internal mechanism of the instrument. In some designs the steam flow meter 
is combined with other instruments. Fig. 262 consists of a steam flow 
meter, to record the amount of steam generated ; an air flow meter, to record 
the amount of air supplied to the furnace ; and a recording thermometer, to 
record the temperature of the uptake or the escaping chimney gases. All 
these readings are shown on a single chart. The steam flow is measured 
by the use of a special orifice, placed between two flanges in the pipe line, 
and corrugated to form its own gasket. Holes are drilled on either side 
of the flange in which the orifice is inserted, and are connected 
with the pressure recording device in the instrument. The air flow part of 



5» 



OPERATION 




Fig. 262. EKag: 






rtrlonal View <^ Bailey Boiler Meter showing 

tz-j-ons and operation of Meter. 



OPERATION 599 



the meter is operated by the difference between pressures in fire box and 
in smoke box. The flue gas temperature is obtained by the aid of a nitrogen- 
filled bulb, extending across the path of the gases where they leave the 
boiler heating surface. The average temperature of all gases is thus obtained, 
and the condition of the boiler heating surface and baffles can be checked. 
The record of steam flow is made in red ink, and that of air flow in blue 
ink. The latter is calibrated so that under ideal conditions the blue and 
red records coincide on the chart. When the air flow pen reads more than 
the steam flow, there is an excess of air passing, and when it reads less, 
the air supply is insufficient ; thus improper conditions can be easily rectified. 



Weighing Coal 

T~'HE equipment for this work may be divided into three classes — that for 
■*■ weighing the coal received, that for weighing the total amount of coal 
consumed, and that for weighing the coal consumed by each boiler unit. 

For checking the amount of coal received at a plant, there are several 
types of equipment, — track scales, wagon scales, weighing hoppers with hand- 
operated or automatic scales, conveyor weighers, and coal meters. For de- 
termining the quantity of coal used each day in a boiler room the same types 
of weighing or measuring devices can be used, and also the movable weigh- 
ing hopper or traveling larry equipped with scale. 

Track scales are set in the car track so that a section of the rails is 
carried by the scale platform, and the railroad cars can be run upon the plat- 
form and weighed. The wagon scale is similar. The coal may be handled 
in small hand-operated industrial cars, automatic railway cars, or cars 
operated by electricity or a cable system. Track scales can be provided to 
weigh the coal handled by such cars, and if the amount handled justifies the 
expense, the scales can automatically record the weight as the car passes 
over the scale platform without stopping. The recording device of one of 
these scales consists of a wheel having the numbers in t\'pe on its periphery, 
and when a lever is moved by the attendant or is tripped automatically as the 
car passes over the platform, the wheel revolves a distance depending on the 
weight, and then prints the amount on a tape which is fed irom one roller 
and wound up on another. The weights of the different loads are thus 
recorded on the tape, which can be taken off whenever desired. 

Track scales are also used for overhead tracks, usually of the monorail 
type. A separate section of rail or rails is supported on the scale beam so 
that the larries or trolleys carrying the loads can be stopped and weighed, 
or if an automatic recording scale is installed, the loads can be weighed as 
they pass over this section of track. 

Fig. 258 illustrates an automatic receiving scale of 75 tons hourly capac- 
ity. This type of scale is very satisfactorily adapted to use in those plants 
where track scales cannot be installed. It operates by the gravity of the 
coal which must be delivered from some point above the scale, and thus 
can take its charges from a hopper, bunker, elevator or conveyor and dis- 
charge into a hopper, chute, conveyor or elevator boot, depending upon the 
service required and the local conditions of handling. 

A crusher is necessary to reduce run of mine coal to reasonably uniform 
sizes for the successful operation of an automatic hopper scale. Where this 
is not done, or where coal is handled on a belt, bucket or pan conveyor, a 
conveyor scale is applicable, and is recommended where head room will not 
admit of a hopper scale. In one type of conveyor scale a section of the 
conveyor is suspended on a floating platform balanced through a compound 
leverage system by an iron float in a cylinder of mercury. For varying 
weights, the float takes up different positions, and its movement offers a 
direct measure of the actual weight on the floating platform. An integrat- 
ing device is used to multiply the weight by the speed of the conveyor. 



600 




Installation of 2500 H. P. of Heine Standard Boilers in the 
Ridgewood Pumping Station, Brooklyn. X. Y. 



OPERATION 



601 




Fig. 258. Richardson Automatic Receiving Scale. 




Fig. 259. Traveling Weigh Hopper. 



6G> 



TION 



For keepir.^ i 't 
devices ordiiiEr'.v e~ 
The automatic 5:i'e r 
the boiler fron:; :r " 



ihe coal after weiffhir.^- 



:dual 
from 



pper ar. 



^ . XQ-J, ^ w 






consist? of s four-wheeled 
T The truck 
tz\ reared 
.:: iz L ;- read 
-r t: : r --rd. 



:. r; ?re usually driren by an electr 
izi'.t'i. 7 t : perator ride? ir. ^ cire 
:;i- It!: trti :o each boiler. 

Thes;: :5 ^tiding fr: : t : tr 
a helical vi: t ?:g. 260. v / ;; f 
of the amiun: :: iur! uiti ly t^:!; 



— i_ 



cica c-i tae 



:t 1 with 
^ guide 
vane is 



. „' — V_ U I 




Fig. 260. Coal Meter of the Heucal Vane Type. 



When stoker fifed, the amo"".: -f coal used by each boiler nuty be 
roughly determined by installine rt : ution counters on the stoker shaft 
With chain grate stolrers the r.p.: I'r.e stoker sprocket must be used in 

conjunction with the depth :: f.rt : _ L:h of grate to get a rough check 
on the coal consumption. I: : rir : kers of the Riley, Taylor or 
Westinghouse type, about 17 t: 1 : f : : :.! : er retort is fed to the furnace 
with each revolution of the crank sna.il. 



OPERATION 



603 



Handling Coal 

THE handling of coal and ashes resolves itself into the following stages: 
(1) Unloading of coal as received, either by land or water; (2) Its 
transfer to bunkers or other storage; (3) Its movement to boilers ready for 
firing; and (4) Removal and final disposal of ashes. 

Unloading of Coal. When the plant Is not large enough to warrant a 
railroad siding the coal is delivered by truck and unloaded by hand. If 
bottom-dumping cars are available, the coal can be discharged directly into 
hoppers or into the storage space provided. With water delivery a clam- 
shell bucket, operated by a locomotive crane or from a tower, can be used 
to move the fuel from the barge. 

Methods of Storing Coal. In small plants the coal may be stored in 
bins, bunkers or piles inside the boiler room ; but in larger plants the quan- 
tities of coal used each day are so large that the inside bunkers hold only 
a few days' supply and outside storage is necessary. 

A convenient storage system often employed is that in which the storage 
space is adjacent to the boiler room and the whole served by a continuous 
bucket conveyor. This bucket conveyor runs horizontally in a tunnel beneath 
the coal storage space and boiler room floor, rises vertically at the far end 
of the boiler room, returns horizontally on a bridge over the boiler coal 
bunkers and outside storage space and finally descends at the outer end of 
the storage pile to the tunnel, thus completely encircling the boiler room 
and storage, Chutes below the coal storage bin deliver the coal to the 




Fig. 263. Circular Coal Storage System. 




o 

■rJ 

CO 
V 

C5 O 



- s 

-< 



:/: 



:z 



X 



OPERATE O N 605 



buckets, which then carry it up above the boiler bunkers where a tripping 
device overturns the buckets and discharges the coal to the bunkers. A con- 
tinuous bucket conveyor installation of this type usually handles ashes as 
well as coal. 

The Circular Storage System, Fig. 263, is often used for storing coal 
for power plant use and is suitable for capacities ranging from 5000 tons up. 
It consists of a long radius locomotive crane equipped with self-filling bucket, 
running on a circular track around a central track hopper into which coal 
is dumped from railroad cars. The coal to be stored is taken from this 
central pit or hopper by the bucket and delivered to the pile. This system 
has a handling capacity of from 40 to 250 tons per hour, according to the 
size of the bucket and crane employed. 

Rectangular Storage. A few large plants store their coal in a pile spanned 
by a traveling bridge. The coal is received in hopper bottom railroad cars 
which discharge into a pit running lengthwise of the pile, from which it is 
removed b}'^ a grab bucket operated from the bridge and placed on the storage 
pile. The capacity of a storage of this type is determined by the span of the 
bridge and length and height of pile. Economical handling capacities of 
storage systems of this type are from 100 to 300 tons per hour. 

Submerged Storage. Bituminous coal which is subject to spontaneous 
combustion is sometimes stored under water. Storage bins for this purpose 
may be constructed of concrete, the inside surfaces being treated with a 
waterproofing compound. A 6000 tons submerged storage pit has been con- 
structed by the Omaha Electric Light and Power Company. The pit is built 
of concrete with walls 22 ft. high on three sides. The fourth wall is 16 ft. 
higher and serves as the support for one rail of the crane runway. The 
other rail is carried by a girder along the side of the power house. Two 
50-ton receiving hoppers, also of concrete, are located at the power house 
end of the submerged storage. 

The storage and spontaneous combustion of bituminous coal are dis- 
cussed on page 466. 

Transfer of Coal from Storage to Boiler Room. Where mechanical 
storage systems are in use, the transfer of the coal from storage pile to car 
is accomplished by means of grab buckets operated from locomotive cranes 
or bridges as described above. However, where mechanical storage systems 
arc not used, and where storage piles are at some distance from the boiler 
room, portable loaders are used to transfer the coal from pile to car or wagon. 
These loaders may be either of the bucket or belt type and may be driven 
by electric motor or gasoline engine. 

Coal can be transferred to the boiler bunkers by small hand or power- 
operated cars, or by a conveyor system. Conveyors may be of several dif- 
ferent types, the selection depending upon the conditions. 

Screw Conveyors may be used for horizontally conveying coal of ^/i 
inch or less, a distance of 100 or 150 ft. The conveyor or screw consists of 
sections of a stamped or rolled steel helix mounted on hollow steel shafting, 
carried by hangers. The screw, which is driven by gears or sprockets at 
one end, revolves in a steel box through which the fuel is conveyed. 

Scraper or Flight Conveyors may be used for conveying fine sizes of coal 
horizontally or on inclines up to about 45 degrees. Single strand conveyors 
of this type consist of a single chain to which are bolted steel flights or 
plates. Double strand conveyors have the flights suspended from two chains, 
and are used when the conveyors are long and subjected to heavy service. 
Either type may be equipped with sliding blocks or rollers. The troughs 
through which the coal is conveyed are made of steel plate or of wood lined 
with plates. 



606 



OPERATION 




OPERATION 



607 



Apron Conveyors are often used for conveying coal horizontally or on 
inclines up to about 30 degrees. Larger sizes of coal may be handled with 
this type than with screw or flight conveyors. The apron conveyor consists 
of two strands of roller chain separated by overlapping apron plates with 
sides from 2 to 6 inches high. These apron plates carry the coal ; and as the 
coal is carried instead of being dragged, less power is required and m.am- 
tenance costs are less than with scraper or screw conveyors. 

Pivoted Bucket Conveyors. Fig. 264, are frequently used in power 
plants. Their use in handling coal from storage to bunkers is discussed 
in a previous paragraph. This type of conveyor will handle comparatively 
large sizes of coal at capacities ranging from 15 to 200 tons per hour. 

Belt Conveyors will handle coal satisfactorily on horizontal runs or on 
inclines up to 20 degrees at capacities up to 500 tons per hour. This type of 
conveyor. Fig, 265, consists of an endless belt driven by suitable pulleys 
and carried upon idler pulleys so arranged that the "carrying" side of the 
belt becomes trough-shaped in cross-section. The loaded or carrying side may 




ua 



RETUnN lOLCftS 



Fig. 265. Belt Conveypr. 



be supported by three or five troughing idlers as may be required, while the 
empty side is carried on straight return idlers. The idlers are carried bv iron 
or wooden stands, spaced from 3 to 6 ft. centers on the troughing side, and 
from 6 to 12 ft. on the return side. The belts generally used consist of 
plies of cotton duck cemented together with a rubber compound and protected 
from moisture and abrasion by a rubber cover. Tripping devices placed at 
the required points discharge the coal from the belt. These trippers are 
mounted on a carriage and consist essentially of two pulleys, one above and 
slightly in advance of the other, so that the belt runs over the upper one and 
under the lower one, thus throwing the coal into a chute on the first down- 
ward turn of the belt. The trippers may be fixed so that the coal will always 
discharge at one point, or movable when it is desired to discharge the coal 
into different bunkers. ]\Iovable trippers may be propelled by a hand-crank 
or automatically propelled by gearing. 

Coal Crushers. When coal is handled by screw or scraper conveyors it 
is necessary to crush the coal down to about ^ inch size. Belt or Inicket 
conveyors will satisfactorily handle larger sizes. 

Coal crushers are generally installed beneath or adjacent to the receiving 
hoppers, see Fig. 263. 

A type of crusher satisfactory for reducing run of mine bituminous coal 
to a size suitable for stoker use, consists of two rolls provided with solid cast 
steel or renewable steel teeth. The rolls are mounted in a heavy frame and 
are gear driven. Relief spring bearings are provided for one of the rolls, 
so that they may separate in case tramp iron enters the crusher. 



608 OPERATION 



Coal Bunkers are generally overhead when mechanical coal handling 
systems and stokers are installed. Usually, overhead bunkers should hold not 
less than one day's supply of coal. In large stations where there are no 
facilities for outside storage, the overhead bunkers may hold as much as a ten 
days' supply. 

Coal bunkers ma}'- be arranged so that each boiler or each batter> has 
its individual bunker, or there may be one continuous bunker for all the 
boilers. Catenary, parabolic and V-shaped bunkers are generally of the con- 
tinuous type. The angle of repose of coal varies from 35 to 40 degrees ; but 
due to convenience in fabricating, the 45 degrees slope is generally used for 
hopper bottoms. Overhead bunkers may be constructed of unlined steel 
plate, of structural steel lined with concrete or of reinforced concrete- 
Down spouts with a shut-off gate convey the coal from the bunkers to 
the firing floor or the stoker hoppers. 

Where overhead bunkers are not installed immediately over the boiler, 
traveling larries, Fig. 258, or traveling buckets, carry the coal from the 
distributing bunker or coal storage to the boiler fronts. 



Ash Handling Systems 

IN all boilers the ashes are either raked out onto the firing floors or are 
dropped into ash pits. The design and construction of ash pits of different 
types of boiler settings is discussed in Chapter 4 on FURNACES AND SET- 
TINGS. 

The pits often discharge into small push or electric cars, which carry 
the ashes to a conveyor or elevator system, from which they are carried to 
the ash bunkers. The coal handling system is used sometimes for carrying 
ashes, although it is considered that the two should be separated, because of 
the abrasive action of the ashes. When the systems are combined, the 
pivoted-bucket conveyor has the advantage that the parts can be replaced 
easily as they wear or corrode. 

The bucket and chain elevator, with rigid buckets, is a common method 
of elevating ashes. The ashes are fed into a boot forming the bottom part 
of the elevator, arc scooped up by the buckets and carried inside a casing 
to the top of the elevator, where they are discharged into a spout leading 
to the point of disposal. This may be an ash bunker, a truck or a railroad car. 

The skip hoist is another well known method of ash removal ; it con- 
sists of a bucket running on inclined or vertical tracks, and hoisted by a 
steel cable attached to a motor-driven winding machine. The bucket and 
chain elevator is recommended for small plants, where the lift is 40 ft. or 
less. For larger plants the skip hoist is said to have the advantages of 
simplicity, low power consumption, and ability to handle the large clinkers 
often produced by forced draft stokers at high overloads. 

Pneumatic Ash Conveyors. These consist primarily of a pipe through 
which a current of rapidly moving air carries the ashes to any desired point. 
Inlets to receive the ashes, consist of tees which are plugged when net in 
use ; and are provided wherever convenient, such as in front of the ashpits. 
The conveyor may discharge onto the ground or into a hopper from which 
cars and wagons may be filled. The commencement of the pipe should 
have an open end, so that there is an ample flow of air along the pipe at 
the first ash inlet. 

In vacuum conveyors, a vacuum is produced in a closed tank, either by 
means of a motor-driven or a steam jet exhauster. When steam-jets are 
used, they may either be arranged to exhaust from a hopper as just described, 
or may be introduced at some point or points after the last inlet, generally 
at a bend in the conveyor pipe. Steam-jet conveyors may either discharge 
into the open or into vented tanks. 



OPERATION 



609 



Since the ash travels at a high velocity, the abrasive action is considerable, 
especially at changes of direction. Therefore, bends are provided with easily 
replaceable "wearing-backs,'" and the ash is generally discharged against 
some form of target to protect the hopper wall. 

Fig. 266 shows one end of the boiler room of No. 2 plant of the Heine 
Company. The inlets of the ash conveyor are flush with the firing Hoor, 
and offer no impediment when closed. The ashes are removed very rapidly 
and the boiler room is kept free from dust and dirt. 




Fig. 266. Detrick-Hagan Steam- Jet Ash Conveyor. 

With hopper ashpits, the conveyor pipe may be laid on the basement 
floor or hung from the underside of the firing floor as is most convenient. 
Connections may also be made to the combustion chambers. 

Clinkers should be broken up and ashes and dust should be dry when 
fed to the conveyor to avoid clogging, particularly at bends. Water sprays 
are frequently placed in the conveyor pipe near the discharge end, or in the 
ash tank. 

Steam-jet conveyors are less noisy than vacuum systems with a steam- 
jet exhauster drawing from the ash tank. It is difficult to muffle these 
latter, owing to the abrasive or "sandblast" action of the fine dust quickly 
perforating metal baffles. 

Flumes. In some plants where there is a plentiful supply of water, 
flumes are constructed beneath the boiler setting, into which the stokers 
discharge their refuse. A stream of water flowing through the flume washes 
the ashes into a pit from which an elevator discharges them to a railroad 
car or wagon. 



610 



OPERATION 



The ash bins used with mechanical conveying sj^stems may be made of 
steel, concrete-lined, or of concrete on a steel skeleton. On account of the 
corrosive action of the wet ashes, concrete or brick bins are often used. 
They should be ventilated to prevent gas explosions. The discharge is from 
the bottom to wagons or railroad cars. 



Handling of Fuel Oil 

HPHE use of fuel oil requires special provisions for storage. While a 
-^ gravity sj^stem of boiler feed is sometimes permissible in small plants or 
in places where large outdoor areas are available for the location of distant 
tanks, the usual practice is to place properly vented cylindrical steel tanks 
under ground or at least below the level of the furnace. 

The arrangement adopted is governed in most instances by local and 
insurance regulations. 

The use of a continuous circulating system, that is, with the surplus oil 
returned to the tank by means of a release valve or by the use of a stand- 
pipe, prevents choking, and is especially important with highly viscous oils. 
The pumps, which are preferably installed in duplicate to protect against in- 
terruption of service, can be either rotary or reciprocating, although the 
former insures a more even pressure. 

Live or exhaust steam heaters are ordinarily used in the pressure line, 
with additional coils in the storage tank if very heavy oils are used. 

Some satisfactory systems for handling fuel oil are the Rogers-Higgins, 
Staples and Pfeifcr, Koerting, Coeii and Moore. Fig. 267, illustrating a 
Rogers-Higgins Oil System, shows the general principles involved. One 
of two duplex oil pumps, mounted on an exhaust steam heater, serves to 
draw the fuel from the storage tank and to force it through the heater and 
strainer to the burners in front of the furnace, where it is atomized by steam. 
The relief valve above the heater carries back the excess oil to the tank 
by a separate line. 




Venfl/ne-,^ 



---Spiral Heater Coil 
Oil Suction-' 
Fig. 267. Diagram of Typical Oil Handling Installation. 

A detailed illustration of the oil pump and heater is shown in Fig. 51, 
on page 125. 



Cleaning Boilers 

THE successful and efficient operation of a boiler demands that the heat- 
ing surface be clean both externally and internally. External cleaning of 
the Heine boiler by means of an efficient mechanical soot blowing system 
has been discussed in Chapter 1 on HEINE PRACTICE. In water tube 



OPERATION 



611 



boilers, the waterlegs of which are not equipped with hollow staybolts, or 
in vertically baffled boilers, the external heating surface is cleaned with a 
hand lance, or the "rotating element" type of mechanical soot blower. 

If boilers are to be stored out in the weather for even short periods, 
the exterior surfaces should be protected with a good grade of red lead or 
black paint. 

To remove the grease and oil which remain from the operation of manu- 
facture, new boilers should be boiled out twice over, with a charge of 2 
to 5 lb. of soda ash each time. 

The effect of scale on heat transmission has been discussed in Chapter 
14 on FEED WATER. It is obvious that the preferable way to keep 
internal heating surfaces clean is to avoid scale formation by proper treat- 
ment of the water before it is fed to the boiler. However, all boiler plants 
are not equipped with water treating systems ; and often, under bad water 
conditions, it is not possible to purge the water of scale-forming materials 
entirely even with chemical treatment. Hence all boilers are subject in a 
greater or lesser degree to scale formation. 

When scale has once formed on the heating surface, it is usual to remove 
it by washing out or by turbining. If chemical compounds are used, care 
must be taken to see that the resulting mud or sludge is blown off, as 
otherwise there is a tendency for it to lodge again on the heating surface 
and cause bagged or blistered tubes. 

Where the scale is of a very soft nature, or where mud deposits on the 
tubes without baking, the heating surface may be effectively cleaned by 
washing out with water. But where the scale is hard, turbining is necessary. 

There are several types of turbine tube cleaners on the market, the most 
satisfactory of which is the water turbine. This, as Fig. 268, usually con- 
sists of a cylindrical casing containing a small hydraulic turbine, with the 
necessary guide plate and turbine wheel. On an extension of the turbine 




Fig. 268. Roto Tube Cleaner. 



shaft arms are mounted to which cutters are attached. These arms revolve 
at high speed and the cutters bearing upon the scale, chip it off the tube in 
small pieces. The stream of water flowing from the turbine envelopes the 
cutters, keeps their edges cool, and washes away the scale as it is loosened. 

It is not advisable to operate turbine tube cleaners by steam, because 
the hot steam exhausting through the tube heats it and causes it to expand 
to a greater length than its cool companions, and this tends to loosen the 
tube expansion in the waterleg, resultmg in leaks. 

Hammer type mechanical tube cleaners, in which the scale is loosened by 
a series of rapid hammer blows, are applicable to either water tube or fire 
tube boilers, but are more generally used for the latter. Care must be taken 
that they are not kept at work in one spot for any length of time, as this 
tends to weaken the tubes by peening bags on them. 

Both hammer and turbine types may be operated by water, steam or com- 
pressed air. 



612 




(U 


o 




• ^H 


o 




o 


«) 




OQ 






-a 


CO 




u 


u 




OS 


fe 




G 


C 




05 


CO 




4-1 

xn 


w 


CO 




*v 


u 


OJ 


TJ 


(U 


.S 


c 


•^ 




JO 





13 
> 


pq 




(U 


-d 


j:: 




Ui 


+-> 





CO 


■$ 


CO 


-d 

c 


tu 

a 




CO 

+-> 
C/2 


a 
'9 


CO 

2 


.s 




G 


"5 


o" 


»-H 








^ 


o 






C 


:3 

CO 


-d 

(U 

a 


.s 


■4-* 


.9" 


*o 


fH 


3 


c 




a* 




iT 


<u 


u 


u 






o 


O 


<u 


a 


CO 


o 




13 


IC 


■M 




<+-. 


15 


(U 


O 


V-c 

CO 


■M 


^ 


> 


CO 

O 

a. 




6 


tj 




.» 


c 


^ 


>> 


CO 


t-c 

o 




o 


^ 


CO 

CO 


ffi 




c 

CO 


S 


4-» 


W 


o 


CO 




+J 




-o 


CO 


CO 


c 


3 


(U 


CO 


U 


CO 

O 




CO 


ffi 




■M 






CO 


g 




m 


o 




'O 


CO 




(U 


3 




_-M 


u 




'H 






D 







OPERATION 613 



Renewing Tubes 

OLD tubes can be removed readily by collapsing the ends of the tube with 
a cold chisel and hammer; but care must be taken not to injure the seat 
in the tube hole. 

When the new tube is in position for expanding, the ends should not pro- 
ject through the tube sheet more than "Ae nor less than ^Ae inch. There are two 
types of tube expanders in use, known as the Prosser and the Dudgeon. 

The Prosser type, which finds favor in locomotive practice, consists of a 
number of steel segments held together by a rubber or spring steel ring. 
These segments are of such a size that when the expander is collapsed, it 
is of smaller size than the bore of the tube, so that it may be inserted easily. 
The segments surround a tapered steel mandrel, by driving which the seg- 
ments are separated and bear against the tube. By gradually driving in the 
mandrel, slacking and turning the tool and driving again, the tube is expanded 
into its seat in the tube sheet. 

The Dudgeon expander, which is widely used in stationary water tube 
practice, expands the tube by the continuous pressure of steel rollers turning 
inside the tube. This type of expander, Fig. 269, consists of a hollow cylin- 
der, with three or more slots in which are steel rollers. A tapered steel 
mandrel is inserted through a central hole in the cylinder and l3ears upon 
the rolls. By revolving the expander and driving the mandrel, the rolls are 
forced outward as they rotate, thus expanding the tube. This expander can 
be either hand or power operated. 




Fig. 269. Henderer-Ferguson Self-Feed Roller Tube Expander. 

After expanding the tube into its seat in the tube sheet, the tube is 
slightly flared. Flaring can be done with a so-called "'belling" tool or by 
using the Dudgeon expander with one steeply tapered roll substituted for a 
straight roll. 

The tubes in water-tube boilers are seldom beaded. When desired this 
may be done with a beading tool or "boot." 

Care of Idle Boilers 

IF a boiler is to be out of service for three or four months it should be 
cleaned thoroughly both internally and externally, by washing out, turbin- 
ing and soot blowing. It should then be filled up with water, to which 100 
or 150 lbs. of soda ash have been added. A slow fire should then be maintained 
until all air has been expelled from the boiler, after which the boiler should 
be pumped full and closed up tightly. If the stack is located directly above 
the boiler, the stack top should be covered, or the lioiler surface so protected 
that rain cannot reach it. 

If the boiler is to be idle for longer than three or four months, it 
should be emptied, turbined, waslied out, left open to dry, and brushed witli a 
scraper or stiff wire brush. A tray of quicklime should then be placed inside 
the drum and the boiler closed up tightly. 



614 OPERATION 



Some engineers, before empt}-ing a boiler that is to be laid up. place 
several gallons of crude oil in the shell, so that when the blow-off or drain 
is opened and the water let out. the oil will form a protecting film on the 
internal heating surface. If this method is used, the boiler must be thor- 
oughly boiled out with soda ash before again being placed in service, so that 
all traces of oil may be removed. 

"Cutting-In" Boilers 

TO "cut-in" a boiler or to put it ■'"on the hne" after it has been out of 
service, is to place it in free communication with other boilers that are 
under steam. 

In cutting in a boiler that has been idle, the stop-valve should be kept 
closed until the steam pressure in the boiler has risen to the exact value 
that is prevailing at the time in the steam main to which the boiler is to 
be connected. It is not sufficient to bring the pressure to within a few 
pounds of that in the main. Practice of this kind should not be tolerated, 
for it is exceedingly important that the equality- should be as exact as the 
engineer can make it b}' the aid of his pressure gages. Then, when the 
equality' is apparently exact, the main stop-valve should be opened very 
slowly and carefully. It should be opened by a mere crack at first, because 
it will be impossible by means of commercial steam-gages to judge the 
equalitv- of the pressure so closely that there will be no flow of steam in 
either direction. The object of opening the valve slowly is to permit the 
small outstanding difference of pressure to become equalized ver>' g^adnall^^ 
If there is an}- evidence of disturbance in the boiler or the piping, as indicated 
by snapping or pounding, or by abnormal vibration of the boiler, the stop- 
valve should be immediately closed again. 

It is safer to have tlie pressure in the boiler that is to be cut in. a little 
higher than that in the steam main, rather than to have it a little lower, 
because steam will then flow from the boiler out into the main instead of 
in the opposite direction. Having the pressure in the boiler exceed that in 
the main, however, is not recommended. It is far better to have the two 
exactly equal. 

Boiler Inspection 

THERE are many engineers who believe that boiler inspection is solely 
the concern of the state or insurance boiler inspector. This attitude is 
not even justified from the consideration of safety only; and it is certainly not 
justified when successful and efficient operation is considered. The engineer 
should not only go over the boiler with the inspector at the time of his 
rather infrequent visits, but should also make it a point to inspect the boiler 
at intervals of a month or two. The inspection of the Heine water tube 
boiler will be discussed here, although the methods of procedure in the case 
of other types will be somewhat the same. 

Before making the actual inspection, the engineer will find it to his ad- 
vantage to have a blue print of the boiler and setting so that he may check 
an}' unusual condition by reference to the print. He will find it necessary' to 
have with him a six-foot rule, a pair of calipers, a stick of chalk, and a 
pencil and note book. An electric light in a guard on an extension cord 
is a desirable part of his equipment, though in lieu of this, a pocket flashlight, 
kerosene torch or candle may be used to furnish light. A mason's hammer 
is a desirable tool to carry, as it can be used for tapping tubes, rivets, etc., 
and also for chipping scale from the heating surface, clinker from the out- 
side of the tubes, etc. 

Inspection of the boiler must be both external and internal. External 
inspection covers the outside of the setting, the inside of the furnace, and 
the exterior of the tubes, waterlegs and shells, while interior inspection refers 
to the examination of the interior side of the boiler heating surface. 



OPERATION 615 



In general, it Is most convenient to make the external examination first, 
for during this part of the work'i a helper may be knocking in man hole 
covers, removing hand hole plates and making ready for internal inspection. 

External Inspection. When examining the exterior of the setting, the 
condition of the brick work should be noted. Cracks and loose bricks 
should be pointed up to prevent air leakage. Inspection doors, fire doors, 
and ash doors should fit tightly. Buckstays should be close to the brick 
v^ork or they are not properly supporting the walls, which is their only 
function. 

Entering the furnace, the grates or stoker parts should be examined. 
Warped or burned grate bars or defective stoker parts should be renewed. 
That part of the furnace brick work subjected to the highest furnace tem- 
peratures should be carefully examined, particularly with reference to erosion 
or to excessive building up of clinker accumulations. Note whether or not 
the brickwork protecting the bottoms of the front and rear waterlegs is 
intact, as these parts should not be exposed to the direct action of flame. 
Scrape the soot and clinker down from the lower baffle and renew such 
tile as are faulty. By holding the light between the rows of tubes near 
each waterleg, look for evidence of leaky tube expansions or leaky staybolts. 
If any are evident, make note of the location by counting the row up 
from the bottom and over from one side, and record the same in the note 
book. 

Enter the setting above the tubes, and drop the light down between the 
rows of tubes near the waterleg and look for evidences of leaky expansions 
as was done from below. Note also the condition of the soot blower ele- 
ments, which should extend at least ^4 J"- and preferably >^ in. through 
the waterleg. If any are burned off flush with the waterleg they should be 
replaced, as the effectiveness of the blast is lessened and erosion of the 
staybolt is liable to result. Look for any soot accumulations which seem to 
indicate that the soot blowers are not effective in cleaning certain portions of 
the heating surface. Examine the upper baffle and make note of any tile 
replacements needed. Inspect the riveted throat connections and shell joints, 
looking for incrustations which may be evidence of leaks. Look carefully 
for external corrosion, such as thinning of tubes, and for commencement of 
cracks near joints in the sheets. Have the helper work the damper rigging 
and note the operation of the damper. This completes the external inspec- 
tion of the boiler. 

Internal Inshection. Before making the internal inspection of the boiler 
BE SURE that : 

(1) The main stop valve is tightly closed. 

(2) The automatic non-return valve is screwed down. 

(3) The blow-off valves are closed. 

(4) The feed water valves are closed. 

(5) The water tender or firemen know you are in the boiler. 

Upon entering the drum, note the thickness or character of the scale 
deposits, and look for evidences of oil along the water line. Chip away 
the scale at every seam, note the condition of the rivet heads and look for 
evidences of corrosion or grooving. Examine the throat stays, and by holding 
the light down into the waterleg, note the condition of the staybolts. In- 
spect the dry pipe, deflection plate and mud drum, and see that they are held 
securely in position. Examine the connections to the water column and see 
that the pipes are clear. 

Examine the staybolts in the waterleg. Tap them with the hammer to 
see if they are tight. Examine the hand hole cap seats, noting whether any 
are cut or grooved, or whether gaskets are sticking. Have a helper hold a 
light at one end of each tube while you examine the tube from the other end. 
Look for piles of loose scale, which, unless removed, may lodge in the tube 
and cause a bag or blister. Note character and thickness of scale. 



616 OPERATION 



After the boiler and furnace have been inspected, the steam gage should 
be calibrated and the water column, blow-off piping and valves should be 
examined. If the safety valves have been repaired or reground, they will 
have to be reset by a responsible operator after the boiler is fired up. 

A report should be made after each inspection and filed for future 
reference. The report will make possible a comparison of the condition of 
the boiler at any time with its condition at former inspections ; and wiU also 
indicate any repairs that are liable to be needed at the next shut-down, so 
that the material may be ordered and be on hand when wanted, thus prevent- 
ing unnecessary delay. 

Cost of Generating Steam 

"pVERY power plant is a business in itself, whether it be a large central 
-^ station or a small isolated plant ; and as a business, its records should 
be kept in such a manner that the cost of producing power is known. 

The object of keeping records is not only to allocate charges for deter- 
mining a fair cost or selling price of the power ; but also to enable the plant 
manager to compare station performance from time to time, and the engineer 
to analyze the various records with a view of reducing all losses to a mini- 
mum. 

Different methods of cost accounting are applicable to dift"erent types of 
power plants. A public utilit}* corporation, which not only generates power, 
but distributes its product over a wide area, will of necessity employ a differ- 
ent cost keeping method than a manufacturing plant which uses its steam 
for power, lighting, industrial cooking, etc. Many states require that pubhc 
utility corporations submit annual statements on printed forms provided by the 
state, and this governs the method of cost accounting to be followed in such 
instances. But the owner of a private plant is free to use his own method 
of cost keeping, and the following general methods of accounting the cost 
of generating steam have been outlined for such cases. 

Power plant costs usually include the total cost of power production, 
with no subdivision of cost into boiler room and engine room expense. For 
example, the labor item is seldom subdivided so as to cover the various 
duties it performs ; yet the necessity of these operations being performed 
creates the expense, and unless it is known how much labor is required to 
perform them, the magnitude and cause of the expense is only approximate. 
The cost of generating steam is the largest factor in power cost, and hence 
it is essential for intelligent management that this cost be kept separate from 
engine room and distribution expenses. 

Costs can be divided into three general classes: (1) overhead or fixed 
charges, (2) operating costs and (3) maintenance costs. 

Overhead Charges 

Overhead or fixed charges may include : 

Interest on Investment Taxes 

Depreciation Insurance 

Rent Management 

Interest on Investment. Expert accountants are not in agreement as to 
the propriety of including this item. It is contended that interest forms part 
of profit, and if included in overhead cost it is virtually charged twice over. 
But in comparing competing equipment, interest on the cost at prevailing 
rates for borrowing money should be considered, so as to make the compari- 
son a fair one. 

Depreciation may be classified as: (1) physical depreciation and (2) 
functional depreciation or obsolescence. 



OPERATION 617 



Physical depreciation is defined as the decrease in value of equipment due 
to age or wear and tear in service, while functional depreciation means the 
decrease in value of equipment due to its becoming unsuitable for use or 
out of date before the end of its estimated life. It is obvious that the rate 
of physical depreciation can be lessened by increasing the life of apparatus by 
repairs and proper maintenance. 

There is considerable disagreement between engineers and between ac- 
countants as to the proper method of computing depreciation charges. 
Probably the most commonly used is the straight-line method which is based 
upon the assumption that if the investment, less the salvage value, is divided 
by the life of the equipment, the resulting quotient expresses the amount 
which should be allowed each year to cover the accrued depreciation. Fre- 
quently the salvage value is not taken into consideration, as being more 
conservative. 

Rental. A proportion of the rent paid for land and buildings should be 
included in overhead charges, unless these are owned by the concern. 

Taxes. The location of the plant governs this item, which may range 
from 0.1 per cent to 2.5 per cent on the assessed valuation of the equipment. 

Insurance may include fire, employers' liability and boiler insurance ; the 
amount being charged to the cost of steam generation, being pro rated to suit 
the particular plant conditions. 

Management Cost is very frequently included in the overhead charges, 
and as such may include a proportion of the following : 

Manager's Time Office Maintenance 

Chief Engineer's Time Restaurant 

Drafting Room Care of Grounds 

Ofifice Help Miscellaneous 

Operating Costs 

Boiler room operating" costs include botli labor and material, wliich 
may be enumerated as follows : 



Fuel 
Water 
Lubricants 
Materials ( Miscellaneous Tools 

Water Softening Chemicals or Boiler Compounds 

Rags and Waste 

Miscellaneous 



Coal Unloading and Ilandling 
Feeding Stokers or Furnaces 
Tending Water 
Cleaning Fire Side of Boilers 
Cleaning Water Side of Boilers 
Labor < Cleaning Economizer 

Cleaning Feed Water Heaters 

Cleaning Boiler Room 

Ash Handling and Disposal 

Testing Boilers 

Miscellaneous 



618 



OPERATION 



Fuel is the largest single item of expense in boiler room operation, and 
therefore any saving effected in its use is readily noted on the cost sheet. 
Labor is the next highest cost of operation. By keeping careful record of the 
distribution of labor in the boiler room, operating costs in this regard 
can be kept down to the minimum necessar}^ for the efficient handling of the 
equipment. An}* undue labor cost in the items enumerated above wUl also 
serve to indicate the advisability of installing more efficient apparatus or labor 
saving machinery. 

Maintenance Costs 

Boiler room maintenance costs also include both labor and material. 
In some respects the line drawn between maintenance costs and operating 
costs is a line one ; though, in general, maintenance is understood to refer to 
the labor and material cost on repairs to : 

Superheaters 
Feed Water Heaters 
Water Softeners 
Pumps and Injectors 



Buildings 

Stacks and Breechings 

Coal Handling Machinery 

Ash Handling ^^lachinery 

Stokers and Furnaces 

Fans and Ducts 

Motors and Stoker Engines 

Boilers and Settings 

Economizers 



Piping, Valves, Traps, Pipe Covering 

Tools 

Instruments 

Miscellaneous 



Maintenance costs tend to increase with the age of equipment. While 
operating costs are low^ered by the installation of labor saving machinery, 
maintenance costs are slightlv increased. 




Four 315 H. P. Heine Standard Boilers set over Jones Underfeed Stokers 
in the Hamilton County Court House, Cincinnati, Ohio. 



619 



INDEX 



A.S.M.E., boiler construction code, 49 
A.S.M.E., boiler testing rules, 513 
Absolute 

temperature, 370 
zero of temperature, 370 
Accounts of steam generation cost, 616 
Acidity of water, see Water 
Adiabatic expansion, 407 
Peahody's diagram, 415 
Air 

admission of secondary, 90 
carbon dioxide 
excess and, 572 
inleakage of, and, 573 
combustion 

actual required, 397 
theoretical required, 394 
composition of, 390 
cooled furnace blocks, 151 
cooling firebrick walls, 151 
currents and insulation, 361 
excess, and weight of gases, 179 
gas weight and excess, 179 
heaters, 339 

air pressure loss in, 339 
humidity, 537 
leakage, 

draft ducts, 236 
settings, 153, 577 
moisture in, 539 

removal in feed water heaters, 329 
required 
per pound of coal, 395 
per 10,000 B.t.u., 189 
with forced draft, 227 
space, 

grates, 58, 97 
setting walls, 145 
specific heat, 403 
water vapor and, weight of, 401 
weight, 182 
saturated, 540 
volume and, 400 
Alberger water meter, 589 
Alcohol thermometers, 373 
Analyses, coal, 440 
Analysis. 
ash, 457 
coal, 450 
fuel, 450 
gas, 532 

conversion of volumetric, 543 



Analysis — Continued 
gas — Continued 

weight of flue gases and, 179 
Anthracite, 436 
briquets, 470 
cleaning fires, 568 
firing low volatile, 563 
forced draft and small, 562 
free burning, 563 
fuel bed thickness, 566 
furnace for hand firing, 95 
grate bars, 97 
hand firing, 562 
heating surface ratios, 562 
high setting, 96 
setting for hand firing, 95 
sizes, 443 

specific gravity, 436 
Arches 

construction, 153 
flat, 153 

smoke and deflection, 93 
Asbestos, 355 

cement for boiler walls, 367 
coating for settings, 157 
conductivity, 353 
heat resistance, 357 
Ash, 457 

analysis, 457 
bins, 610 

boiler testing, 536 
coal, in 

evaporation and, 459 

heat value and, 458 

reducing, 458 
combustible in, loss, 545 
composition, 457 
conveyors, 608 

flume, 609 

pneumatic, 608 

steam jet, 608 

vacuum, 608 
determination, coal analysis, 451 
effect on firebrick, 151 
elevators, 608 

fusibility in U. S. coals, 463 
fusion, 461 

Illinois coal, 462 

Indiana coal, 462 
handling, 608 
hoists, 608 
Ashpits, 107 
capacity, 107 



620 



I X D E X 



Ashpits — Continued 

combustion in, 111 

doors, 111 

hand firing. 107, 109 

hopper, 109 

large capacit}', 109 

leaky doors. 111 

Hning of hopper, 111 

side feed stokers, 109 

valves, HI 
Atmosphere, composition of, 390 
Atomic weights, 350 
Atomizing oil fuel, 119 
Auxiliaries 

exhaust to feed heaters, 326 

regulation of exhaust to feed heater, 
326 

steam used by, 423, 547 
Auxiliary 

engines, 341 

fuel bed for blast furnace gas, 129 

turbines, 341 

B 

Badger expansion joint, 290 
Baffles, 

deflecting, in flues, 217 

divided pass, 65 

flues, in, 217 

forming furnace roof, 65 

soot blowers and, 65 

tight, keeping, 65 

tiles, 66 
Baffling, 59 

boiler efficienc}- and, 63 

chimney temperature and. 63 

draft loss and, 62 

exit gas temperature and, 63 

extinguishing action with vertical, 93 

flue gas temperature and, 63 

furnace temperature and. 87 

head room for vertical, 91 

Heine boilers, 27 

smoke and horizontal. S7 

stack temperature and, 61 

vertical, and head room, 91 

waste heat boilers, 141 
Bagasse 

burning, 137 

composition, 477 

grate bars for, 99 

grates. 137 

heat value, 475 
Bailey boiler meter, 598 
Balanced draft, 584 
Banked fires, 568 

fuel consumption by, 568 

quick steaming from, 568 
Bark, see Tan bark 



Barometer 
boiler testing and. 536 
chimneys and height of, 173, 192 
Bends, expansion pipe, 287 
Best Calorex oil burner, 121 
Birkholz-Terheck gas burner, 130 
Bituminous coal, see Coal, bituminous 
Blast furnace gas, 128 
boiler setting, 128 
burners, 130 
burning. 128 
comoosition, 483 
dust; 129 
explosions, 129 
heat valucj 483 
igniting grate, 129 
Blow down of safetv valves, 554 
Blowins: soot, 39. 4L 610 
Blow-off 
piping, 275 
valves, 274, 560 
Boiler, 
capacity and economy, 66 
circulation. 66, 568 

Heine, 35, 43 

quick steaming and. 568 
compounds, 510 

construction, A. S. M. E. code. 49 
drums, heat insulation of, 157 
efficiency-, 546 

baffling and, 63 

carbon dioxide and. 572 

characteristics, 66 

clinker and, 461 

superheating and, 69 

with two stokers, 105 
feeding, see 

Centrifugal boiler feed pumps 

Feed pumps 

Feed water heaters 

In lectors 

Water 
fittings. 551 
Heine cross drum, 43 
horsepower, 55 
inspection. 614 

precautions, 615 

report, 616 
operation, 

economical, 584 

under *"test conditions."' 585 

waste heat, 142 
plant depreciation, 616 
rating. 5S 

room basement, 110 
settings. 85 

air leakage. 153 

air leakage and CO2. 573 

air leakage, curing. 577 

air leakage, prevention, 157 

air leakage, testing for, 577 



INDEX 



621 



Boiler — Continued 
settings — Continued 

air space in walls. 145 

air-tight, for waste heat, 142 

anchor rods, 148 

anthracite, 95 

arches in, 153 

asbestos coating, 157 

bagasse, 137 

blast furnace gas, 128 

brick required for, 147 

brickwork, 145 

buckstays, 148 

cargo boats, 143 

chain grate stokers, 100 

classification, 92 

concrete, 147 

down draft, 95, 100 

draft loss. 186 

dredge boat, 143 

fireclay mortar, 147 

foundations, 145 

front feed stokers, 101 

gas burning, 127 

glazed brick, 156 

high smokeless, 91 

insulating, 155 

insulating brick, 155 

magnesia coating, 157 

marine, 143 

oil burning, 117 

over feed stokers, 101 

powdered coal. 111 

radiation, 153 

refuse burning, 133 

shavings, 134 

side feed stokers, 100 

smokeless, 93 

steel casing, 156 

stokers, 100 

stokers, two, 105 

tie rods, 148 

underfeed stokers, 103 

walls, 145 

wall ties, 155 

waste heat, 139 

wood chips, 134 

wood chips and coal, 134 
specifications, standard, 49 
testing, 513 

accuracy, 515, 547 

air temperature, 531 

ashes and refuse, 536 

ashes, combustible in, 545 

barometer, 536 

calculating heat balance, 542 

calculating simple test, 528 

calorimeter, Carpenter, 522 

calorimeter, coal, 455 

calorimeter, gas, 482 

calorimeter, Junker, 482 

calorimeter, Mahler, 455 



Boiler — Continued 
testing — Continued 

calorimeter, Peabody, 518 

calorimeter, separatmg, 522 

calorimeter, throttling, 518 

carbon monoxide loss, 545 

Carpenter calorimeter, 522 

chart, 526 

coal sampling, 517 

coal weighing, 517 

condition of boiler, 515 

data required, 515 

draft gages, 536, 579 

efficiency, boiler, 546 

efficiency, furnace, 546 

efficiency, overall, 546 

errors, 547 

exit gas temperature, 529 

factor for moisture in steam, 528 

factor of evaporation, 528 

feed water temperature, 517 

feed water weighing, 515 

flue gas analysis, 531 

flue gas heat loss, 543 

flue gas temperature, 529 

furnace temperature, 536 

gas analysis, 532 

gas analysis apparatus, 532 

gas analysis, conversion, 543 

gas sampling continuous, 532 

gas sampling tubes, 531 

gaseous fuel, 550 

guarantee tolerance, 547 

hand firing, 523 

heat balance example, 546 

heat balance form, 541 

heat losses, 542 

Hempel apparatus, 535 

humidity of air, 536 

humidity tables, 537 

hydrocarbon loss, 546 

hydrogen loss, 543, 546 

leakage of water, 516 

liquid fuel, 550 

log book. 526 

losses unaccounted for, 546 

mechanical stokers, 525 

moisture in air, 536, 539 

moisture in air, loss by, 545 

moisture in coal, loss by, 542 

moisture in steam, 518 

observations, 525 

Orsat apparatus, 532 

Orsat operation, 533 

Peabody calorimeter, 518 

personnel, 513 

radiation loss, 546 

records, 525 

report of complete test. 540 

report of simple test, 526 

sampling" coal, 517 

sampling gas, 531 



622 



INDEX 



Boiler — Continued 
testing — Continued 

sampling steam, 323 

separating calorimeter, 522 

starting and stopping, 523 

steam pressure, 518 

steam quality, 518 

steam tables, 523 

superheated steam, 523 

temperature of air, 531 

temperature of feed water, 517 

temperature of flue gases. 529 

temperature of furnace, 536 

throttling calorimeter, 518 

unaccounted for losses, 546 

water gages, 516 

water meters, 516, 587 

weighing coal. 517 

weighing feed water, 515 

weighing scales, 517 

weight of gases. 543 
the first Heine, 52 
tubes, conductivity. 383 
wall insulation. 367 
water gages. 516, 551 
with two stokers, 105 

Boilers, 

air-tight settings for waste heat, 142 
baftling, 59 

waste heat, 141 
blowing soot. 610 

Heine, 39, 41 
cleaning, 610 

Heine, 21, 39, 41, 43 
convection and heat transfer. 385 

in waste heat, 141 
corrosion in marine, 49 
"cutting in." 614 
dead gas pockets. 59 
draft loss, 62, 186 

waste heat, 142 
dusting. 610 

dust in waste heat, 142 
fans for waste heat. 142 
feed water heating in Heine, 35, 45 
gas pockets in, 59 
heat transfer, 389 

waste heat, 141 
Heine 

cross dnim, 43 

longitudinal drum. 23 

marine, 47 
high draft loss, 142 
high eas velocit>', 141 
idle, 613 

stand-by. 568 _ _ 

steam separation in Heine, 35, 43 
temperature drop in, 389 
waste heat. 139 

water purification in Heine, 19, 35, 45 
zinc plates in marine, 49 



Boiling point of water at different pres- 
sures, 500 
Bomb calorimeter, 455 
Bonnot powdered coal system, 112 
Bourdon pressure gage, hhh 
BradshaiL'-Fraser gas burner, 131 
Brady {Harrington) stoker, 168 
Breechings, 214 

arrangement, 219 

baffles in, 217 

cleaning doors, 217 

construction, 217 

design, 215 

draft loss through, 187 

example of, 218 

insulation, 220, 367 

size of, 214 
Brick 

arches, 153 

boiler settings, 
glazed, 156 
insulating, 155 
vitritied, 156 

chimnevs, 201 

hre. 148 

plastic fire, 152 
Bricks, number of, for settings. 147 
Brickwork 

boiler settings, 145 

smokeless combustion, 85 
Bridgewall 
" cleaning table, 567 

gas passage area over, 93 
British thermal unit, 378 
Briquets, 469 

anthracite 470 

carbocoal, 471 

lignite, 471 

peat, 471 

weight of. 466 
Buckstays, 148 
Bunkers, coal, 608 
Burners. 

gas, 128 

oil, 119 

powdered coal, 116 

tar, 125 
Burning superheaters. 76, 555 
Buying fuels under contract, 486 

C 

Calibrating 

p3Tometers, 370 

thermometers, 370. 373 

water meters. 516 
California oil. heat value. 479 
Calorex oil burner, 121 • 

Calorimeter. 

bomb. 455 

Carpenter separating, 522 

coal. 455 

formula for throttling, 521 



INDEX 



623 



Calorimeter — Continued 

gas, 482 

Junker gas, 482 

Mahler bomb, 455 

Peahody steam, 518 

separating, 522 

steam connection, 523 

throttling, 518 
Campbell's coal classification, 437 
Cannel coal, 437 
Carbocoal briquets, 471 
Carbon 

combustion data, 393 

determination in coal, 451, 453 
Carbon dioxide 

boiler efficiency and, 572 

careless firing and, 572 

excess air and, 572 

desirable percentage, 572 

dirty fires and, 575 

leaky settings and, 573 

recorders, 577 

specific heat of, 403 

weight of flue gases and, 179, 543 
Carbon monoxide 

combustion data, 393 

heat loss due to, 545, 577 

recorders, 578 

specific heat, 403 
Carpenter calorimeter, 522 
Cast iron, 

effect of heat on, 97, 252 

for grates, 96 

strength of, 97, 271 

superheated steam and, 83 
Cast steel and superheated steam, 83 
Caustic embrittlement, 511 
Causticity of feed water, 503. 505 
Celsius temperature scale, 369 
Cement, 

plastic fireclay, 152 

settings coated with asbestos, 157 
Centigrade temperature scale, 370 
Centrifugal boiler feed pumps, 302 

capacity, 305 

characteristics, 303 

DeLaval, 306 

efficiency, 305 

horsepower, 305 

hot water capacity. 318 

Lea-Court enay, 307 

motor-driven, 313 

regulating. 313 

single-stage, 306 

turbine driven, 305, 345 

with low-pressure economizer, 306 
Check valves, 274 
Chimneys, 173 

anthracite, 173 
. at altitudes, 192 



Chimneys — Continued 

B.H.P. and draft table, 176 

baffles in, 217 

brick, 

ladders on, 206 

lining for, 205 

radial, 201 
capacity table, 176 
characteristics, 177 

cinders, discharging, 207, 208, 240, 572 
cleaning doors, 195, 207 
coal burned, weight of, 185 
coal burning, 

anthracite, 173 

western, 184 
concrete, 207 

design of, 209 

erection of, 210 
connections for 

flues, 214 

induced draft fans, 241 
cost by height, 173 
defective, strengthening. 214 
deflectors in, 217 
draft 

capacity and. 181 

H.P. and, table, 176 

losses tabulated, 187 

loss in, 182 

required. 187 
evase, 191 
examples, 184 
flue openings in, 214, 241 
foundations, 193 

sizes, 194 
gas basis, design on, 189 
gas burning. 190 
gases, 

heat of fuel in, 334, 543 

weight of. 182, 543 
guyed steel. 197 
H.P. and draft table, 176 
height, 

anthracite, 173 

cost and, 173 

economical, 173 
highest, 173, 216 

concrete, 211 
joints in steel, 200 
ladders, 

brick, 206 
_ steel, 195 
lightning rods, 206 
lining, 

brick, 205 

steel, 195 
municipal refuse, 191 
oil burning. 189 
power plant typical, 184 
pressure of wind, 193 



624 



INDEX 



Chimneys — Continued 
radial brick, 201 
refuse, municipal, 191 
reinforced concrete, 207 
reinforcing old brick, 213 
remodeling, 214 
self-supporting steel. 194 
soot collectors in, 207 
steel, 
guyed, 197 
joints in, 200 
ladders on, 195 
lining for, 195 
self-supporting, 194 
strengthening defective, 214 
stoker firing. 1S4 
table, draft and H.P., 176 
temperature, 
drop in, 174 
gases, average. 181 
topical power plant, 184 
velocity- of gases in, 189 
venturi. 191 
wind pressure on, 193 
wood burning, 191 
Cinder separating fans, 237, 572 
Cinders from chimnej-s. 572 
Circulation, see Boiler circulation 
Cleaning 
boilers, see Boilers, cleaning 
coal, 458 
fires, 567 
anthracite. 568 
COs and. 575 
table, 567 
Cleveland stoker, 159 
Clinker, 459 
adherence, 151 
avoiding, 466 
boiler efficiencv and, 461 
hard, 459 
Illinois coal. 462 
Indiana coal. 462 
soft. 461 
sticking, 151 
U. S, coals, 463 
Coal, 
air required, 395 

per 10,000 B.t.u., 189 
analyses, 440 
analysis, 450 

statements, 450 
anthracite, 436 
ash, 
and heat value of, 458 
fusibilitj.-. 463 
reduction in. 458 
bituminous, 436 

fuel bed thickness, 566 
hand firing, 560 
briquets. 469 



Coal — ^Continued 

bunkers, 608 

burners for powdered, 115 
burning powdered, 111 
bu3-ing under contract 486 
calorimeter, Mahler, 455 
cannel, 437 
carbon in, 453 
classification, 

composition, 437 

geological, 435 
clinker, 459, 562 
composition, 435, 440 
consumption, 

banked fires, 568 

stand-by boilers, 568 
conveyors, 605 

apron. 607 

belt 607 

flight, 605 

pivoted bucket, 607 

scraper, 605 

screw, 605 
crushers, 607 
draft for, 185 
evaporation and ash in. 459 

composition, 483 

heat value of, 483 
gases, weight of flue, 543 
geological classification, 435 
hand firing, 

anthracite. 562 

bituminous. 560 
handling, 603 

see Coal conveyors 
heat value by 

analysis, 453 

calorimeter, 455 
hydrogen in. 453. 543 
location of deposits, 437 
meter, helical vane, 602 
moisture in. 

analysis, 450 

errors. 547 

loss due to. 542 

sampling, 517 
nitrogen in, 453 
oxygen in, 453 
powdered, 

burners, 115 

burning. 111 
proximate analysis. 451 
sampling, 445 

boiler testing. 517 

errors. 547 
semi-anthracite. 436 
semi-bituminous, 436 
sizes of 

anthracite. 443 

bituminous. 445 



I N IJ E X 



625 



Coal — Continued 

specifications, 486 
spontaneous combustion of, 467 
spouts, 60S 
storage, 603 
circular, 605 
deterioration, 467 
rectangular, 605 
submerged, 605 
sub-bituminous, 436 
sulphur in, 451, 463 
-tar, see Tar 
ultimate analysis, 451 
unloading, 603 
volatile matter, 451 
volume, 467 
washing, 458 

weighing, see Boiler testing- 
continuous, 599 
conveyor scales, 599 
helical vane, 602 
hopper scale, 601 
hopper, traveling, 601 
stoker speed, 602 
track scales, 599 
traveling hopper, 601 
traveling larry, 602 
weight of, 466 
Cochrane feed water heater. 325 
Cochrane water softener, 509 
Cocn oil burner, 123 
Coke, 
breeze, 474 
composition, 473 
heat value, 473 
-oven gas, 
burning, 131 
composition, 483 
heat value, 483 
weight of, 474 
Colloidal fuel, 481 
Combustion, 389 
air required, 
actual, 397 
theoretical, 394 
ashpit, 111 

liaffle furnace roof and, 65 
chamber, 85 

blast furnace gas, 128 
gas passage arens. ^3 
Heine boilers, 21, 37 
natural gas, 127 
oil, 117 
shape of. 90 
size of. 85 

surface, oil Imrning, 117 
temperature, 86 
chemistrv of, 390 
data, 393 
furnace 

temperature and, 86 



Combustion — Continued 
furnace — Continued 

volume and, 87 

heat of, 394 

losses, 397 

rate, 57 

requirements, 85 

space, 

grate area and, 89 
required, 85, 89 

spontaneous, of coal, 467 
Combustion Eng. Co., Type "E" stoker. 

161 
Concrete 

boiler settings, 147 

chimneys, 207 
Condensers, heat transfer in. 389 
Conduction of heat, 379, 383 
Conductivity, 

boiler tubes, 383 

insulation, 155 

materials, 351 
table of, 353 

refractories. 155 
Cones, Seger, ?)77 
Continental stoker, 167 
Control boards, 584 
Convection, 379. 385 

waste heat boilers, 141 
Convevors, wood refuse and pneumatic, 
133 

see Coal conve}ors. 
Copes' feed water regulator, 314 
Cork heat insulation, 357 
Corn, heat value, 474 
Corrosion, 

feed pumps, 301 

feed water and, 510 

.gases in feed water and, 503, 510 

marine boilers, 49 
Cost 

accounts of generating steam. 616 

boilers 1)y lieating surface, 57 

comparison of lioiler feed pumps, 305 

reducing", of generating steam. 5S7 

reduction, Polakov method of power, 
585 
Co.ve stoker, 168 
Crushers, coal, 607 
Culm, grate bars for. 97 
"Cutting-in" boilers, 614 

D 

Danu^^ers, 220 
l)alancing. 222 
design, 221 
details, 222 
forced draft, 235 
induced draft, 241 
o]ieration of. 222 
regulators, 584 



626 



INDEX 



DtLaial centrifugal feed pump, 306 
Depreciation of boiler plant. 616 
Destructor chimneys, refuse. 191 
Detrick-Hagan ash conveyor, 609 
Detroit stoker, 159 
Diatomaceous earth, 2>^7 
Differential draft gages, 580 
Disengaging surface, steam, 67 
Down draft furnace, 95, 100 
Draft 
anthracite, small, 173, 562 
balanced, 584 
chimney capacity and, 181 
coal burning, 185 
diagrams, 22?) 
ducts, forced, 235 
air leakage, 236 
forced, 227 
sras^ss 
boiler testing, 536 
choked passes. 581 
compound. 580 
connections, 580 
diaphragm. 580 
differential. 580 
flow meter, 581 
liquid for, 580 
multiple. 580 
poor fires. 581 
simple. 579 
slanting tube. 580 
small pressure differences. 580 
gas burning. 190 
induced. 236 
instruments, 579 
lignite. 566 
loss. 

accelerating gases. 187 
air heaters, 339 
altering gas velocity, 187 
baffling and, 62 
boiler setting, 186 
chimneys. 182 
economizers, 186 
flues. 182. 187 
fuel bed 185 
waste heat boilers. 142 
losses tabulated. 187 
mechanical, 223 
oil burning. 189 
pressures, forced. 227. 231 
regulators, 584 
table, chimneys. 176 
wood burning, 191 
Ducts, forced draft. 235 

air leakage in. 236 
Dudgeon tube expander. 613 
Dulotig formula. 454. 479 
Dumping srrates. 97. 568 
Dust 
blast furnace gas. 129 



Dust — Continued 

blowers 

baffles and, 65 
boilers, 39.' 41, 610 
economizers. 333 
superheaters. 31 
doors, leaking, 153 
separating fans. 237 
waste heat boilers, 141 



Earth, diatomaceous, 357 
Economizers. 331 

counter flow. 334 

dimensions, 337 

draft 

diagram. 225 
loss through, 186 

Green, 333 

heating surface, 337 

heat 

recovery- by, 335 
transfer rate. 335 

integral, 331 

low pressure, 306 

performance, 333 

saving effected by, 333 

scrapers. 333 

soot blowers. 333 

steel tube. 331 

surface. 337 
Electrical pyrometers. 373 
Electrohsis and corrosion. 510 
Embrittlement. caustic, 511 
Engines. 

auxiliary. 341 

fan. 343 

pump. 309 

stoker, 343 

superheated steam. 69 
Entropy. 407 

diagrams. 414 
Peabody, 415 
MolUer, 416 
superheated steam. 69 
Equivalent 

evaporation. 55. 528 

mechanical, of heat. 378 
Erosion of turbine blades. 73 
Eschka's method for sulphur, 451 
Evaporation 

ash in coal and, 459 

equivalent. BS. 528 

factor of. 55, 528 

rate. 57 

rate and circulation. 66 
Evase chimneys, 191 
Everlasting blow-off valve. 560 
Excess air. 

carbon dioxide and. 572 

general etTect. 575 



INDEX 



627 



Excess air — Continued 

weight of gases and, 179 
Exit gases, see Flue gases 
Expansion, 
adiabatic, 407, 414 
firebrick, 149 
force of, piping, 286 
isothermal, 407, 414 
joints, 286 

metals, coefficients, 283 
nozzles, 417 
pipe bends, 287 
piping, 283 
steam, 407 
Explosion doors, 129 
Explosions with blast furnace gas. 129 
Extinguishing action with vertical baf- 
fling, 93 

F 
Factor 

for moisture in steam, 528 
of evaporation, 55. 528 
Fahrenheit scale, 370 
Fans, 

characteristics, 229 

chimney connections for induced draft, 

241 
cinder separating, 237, 572 
dampers for 

forced draft, 235 
induced draft, 241 
densitv of gases with induced draft, 

239 
dirt unbalancing, 229, 236 
drives, 228 
ducts, 235 

efficiency, induced draft. 240 
engine and feed pump, 309 
engines, 343 

erosion, induced draft, 236 
forced draft, 227 

ducts, 235 
H.P. output, 235 
inlet screens, 236 
load on induced draft, 239 
operating difficulties, 229 
output. 235 
performance, 232 
pitot tube, testing. 232 
safe tip speed, 232 
screens, 236 
sizes 

forced draft, 228 
induced draft, 237 
speed, 

induced draft, 237 
safe, 232 
test, 232 
testing, 232 

induced draft, 240 
pitot tube, 232 



Fans — Continued 

turbine driven, 227, 343 

types of, 229 

waste heat boilers, 142 

water-cooled bearings, 237 

weakened by heat, 239 

weight, 

forced draft, 228 

induced draft, 237 

Feed pumps, 297 
air chambers, 298 
automatic regulation, 310 
bronze fittings, 301 
capacity, 

duplex, 299 

hot water, 299, 317 

simplex, 298 

single cylinder, 298 
centrifugal, see Centrifugal boiler feed 

pumps 
corrosion, 301 
cost comparison, 305 
direct acting 

power, 309 

steam, 297 
duplex, 299 
excess pressure, 297 

regulator, 310 
knocking, 299 
motor driven, 311 

regulator, 311 
performance, 301 
piston speed, 299 
power driven, 309 
pressure regulator, 310 
regulation, 313 
"short stroking," 298, 299 
simplex, 298 
single cylinder, 298 
"steam bound," 299 
steam consumption, 302, 305 
suction lift, 317 

hot water, 317 
suction piping, 318 
triplex. 309 

volumetric efficiency, 298 
Feed water, see Water 
constant excess pressure, 310 
economy of heating, 323 
heaters, 323 

closed, 327 

Cochrane, 325 

filter, 326 

metering, 325 

oil separating, 326 

open, 323 

Patterson-Berry man, 327 

regulation of exhaust steam to. 326 

removal of air in, 329 

selection of, 330 



628 



INDEX 



Fee! :er — Continued 

! ei: :::^ in 
Heine boilers, 35, 45 
ice plants. 329 

purification in Heine boilers. 19 

quantity required. 297 

regulators. 310 

5:e:-m required to heat 325 
7elr. jiair. 357 

Ferguson tube expander, 613 
Fery pjTometer, 377 
Filters. 

feed water heater. 326 

wster treatment. 50S 
?;rr r :■: 148 

a r-: :ed blocks. 151 

blocKs, 

air-cooled. 151 
-e-f: rated. 151 
c : :: errial. 149 

-ion of. 149 
e T : : ash on. 151 

n of. 149 
f . I'int 149 
h r e 5. 149 

-:::;:e."r;.::r:f 149 

plastic. 152 

plasticity of. 14S 

special blocks. 148 

standard shapes. 150 

surface, oil burning. 117 

weight of. 151 
Fireclay. 148 

cements, plastic. 151 

mortar. 151 

plastic cement. 151 
Fire 

ashpit, in. Ill 

cleaning. 567 

protection and stand-b^- boilers, 568 

sand. 151 
Fires, banked, 568 
Firing 

carbon dioxide and. 574 

tools. 563 
Flexible metallic pipe. 293 
Flooding superheaters. 76 
Flow meter 

draft gage as. 581 

Repuhlie, 594 

steam. 595 

variable orifice. 597 

water. 594 
Flow of steam. 

Grashof, 421 

Xal*ier, 421 

nozzles. 417 

P,>0.58P,. 421 

Rateau, 420 



Flue gases, 
air heaters. 339 
analysis. 531 

apparatus. 532 

conversion to weight. 543 

Orsat. 532 
heat of fuel in. 334 
loss due to CO in. S45 
loss due to heat in. 543 
sampling, 

-'■ 531 
: rure. 178. 529 

-g and. 61. 63 
e- e:-cy and. 574 
- : tr vr Tine and. 69 
-^:: f. 182. 543 

Dairies in. 217 
cleaning doors. 217 
f : - -tion of. 217 
r : rs in. 217 
design of. 215 
ex-T^nle of. 218 
:: ?s. 182. 187 
ir^UiaLion, 220 
size. 184. 214 
V e-r-und. 220 
r!. ; rr _ nreclaj- mortar, 151 
Foaming and bad water. 510 
Foersi oil burner, 121 
Forced draft, 

air required. 227 
ducts, 235 
fans, see Fans 
pressures. 227 
Foundations. 

boiler settings. 145 
chimney^s. 193 
Fraser's coal classification, 437 
Fuel. 435 

air required. 395 
analysis. 450 

bed thickness, see fuel in question 
buying under contract. 4S6 
classification of solid, 435 
coUoidal. 481 

consumption, banked fires. 568 
errors in moisture in, 547 
gaseous. 4S2 

heat value, see fuel in question 
high. 485 
low. 485 
wet, 477 
hydrogen loss. 543 
liquid. 478 
loss due to 

hxdrogen in, 543 
moisture in. 542 



INDEX 



629 



Fuel — Continued 

moisture in, 

errors, 547 

tinding, 450, 517 

loss by, 542 
oil, see Oil 
sampling, 445 

boiler testing, 517 

errors, 547 
suDerheating, extra for, 69 
weight of gases, 543 
wet, heat value of, 477 
Furnaces, 

air-cooled lining, 151 

arches, 153 

l)affle roof, 65 

boiler settings and, 85 

chamber, gas passage areas, 93 

design of, 85 

down draft, 95, 100 

gases from industrial, temperature of, 

141 
industrial, temperature of gases from, 

141 
linings, air-cooled, 151 
oil burning, 119 

smoke and down draft, 95, 100 
smokeless, 93 
temperature, 

complete combustion and, 86 

observing. 536 

theoretical, 394 

tile roof and, 87 
volume, see fuel in question 
Fusible plugs, 560 
Fusion of 
ash, 461 
firebrick, 149 

G 
Gage, 
boiler water, 516, 551 
piping, boiler water, 551 
Gages, 
see 

Draft gages 

Pressure gages 
Gas, 
see 

Blast furnace gas 

Coal gas 

Coke-oven gas 

Flue gases 

Natural gas 

Oil gas 

Producer gas 

Water gas 
analysis, 532 

CO recorders, 578 

CO2 recorders, 577 

Hempcl apparatus, 535 

Orsat apparatus, 532 



Gas — Continued 

burners, 128 
burning, 127 

settings. 127 
calorimeter, 482 
passage area, 59, 93 
pockets, dead, 59 

producer and superheated steam, 83 
sampling, 

errors, 547 

flue, 531 
temperature drop, 

chimneys, 174 

over heating surface, 3S>7 
velocity, 

heat transfer, 385 

waste heat boilers. 141 
Gaseous fuels, 482 
Gases, 
density of. 399 

in feed water and corrosion. 503. 510 
pressure effect, 398 
properties, 398 
specific heat of, 399. 401 
temperature effect, 398 
volume, 398 
weight, 398 
Gate valves, 273 
Globe valves, 273 
GoodcnougJi's steam taldes, 424 
Graphite. 436 

Grashof, flow of steam, 421 
Grate, 
air space, 58, 97 
bar openings, 58. 97 
bars, 

anthracite. 97 

bagasse, 137 

cast iron for, 96 

culm, 97 

heat effect on cast iron, 97 

lierringbone, 97 

hollow, 99 

slotted, 97 

Tupper, 97 
hand firing, 96 
inclination 100 
length, 99 
slope. 100 
surface, 57 

anthracite, 562 

ratio, 58. 562. 567 
water. 95, 100 
Green economizer, 333 
Green stoker, 168 
Gu\-s for steel chinmeys. 201 

H 

Uas:aii ash convcvor, 609 

Mair felt, 357 

Ilnnniiel oil burner, 120 



630 



I X D E X 



Hammond water meter, 589 
Hand firing, 560 
anthracite, 562 
low volatile, 563 
setting, 95 
ashpit, 107 

large, 109 
CO2 and, 574 
coal cars, 563 
depth of grate. 99 
frequency, 565 
grates, 96 
losses, 565 
methods, 560 
rules, 561 
space for, 563 
thickness of fire, 566 
tools. 563 
Handhole caps, Key, 27, 47, 54 
Hard coal, see Anthracite 
Harrington stoker, 16S 
Hays draft gage, 580 
Head room, 

furnace for soft coal. 90 
smokeless settings. 91 
stoker settings, 100 
vertical baffling, 91, 93 
Heat 
balance, 

calculating. 542 

example, 546 

form of, 541 
combustion, of, 391 
conduction, 383 
convection. 385 
effect on strength of materials. 97. 239. 

252 
insulation. 347 

air currents. 361 

breechings, 220. 367 

boiler drums, 157. v365 

boiler settings, 155, 367 

cold water pipes. 367 

commercial, 354 

conductivity, 156. 353 

cork, 357 

econom}-. 349 

efficiencv. 360 

flues. 220, 367 

hair felt, 357 

loose, 361 

''magnesia. 85%,"' 357 

painting, 361 

pipe size and, 360 

piping, 360 

piping, outdoor, 367 

piping in trenches, 367 

piping in tunnels, 367 

piping, underground, 367 

settings, 155 

surface finish. 361 

surface resistance, 347 



Heat — Continued 
insulation — Continued 

thickness, 360 

uses of, 355 

walls, 2)67 

waste without, 349 

weight of, 355 
loss, 

bare surfaces, 348 

CO in flue gases. 545, 577 

combustible in ash, 545 

commercial insulators, 354 

hydrocarbons, 546 

hydrogen, 543 

moisture in air, 545 

moisture in coal, 542 

radiation, 546 

soot formation, 547 

unaccounted for, 546 
losses, see Heat balance 
mechanical equivalent of, 378 
radiation, 379 
resistance, 385 

asbestos. 357 
specific, 378 

gases, 399 
theorv, 369 
transfer, 58, 378 

air heaters, 339 

boilers, 389 

condensers, 389 

convection, 385 

economizers, 335 

gas velocity and, 385 

insulation, 359 

scale and, 511 

superheaters, 81 

surface resistance, 347 

waste heat boilers, 141 
treatment, feed water, 507 
units, 378 
values, see fuel in question 

Diilong formula, 454, 479 
Heaters, 
air, 339 

feed water, see Feed water heaters 
Heating surface, 57 
cost of boilers b}', 57 
economizer, 337 
evaporation rate, 57 
gas temperature drop over, 387 
ratios, 58 

anthracite, 562 
tan bark. 567 
Height of furnace chamber and 
smoke, 90 

stoker settings, 100 
vertical baffling, 93 
Heine 
baffle tile, 66 
boiler, the first, 52 



INDEX 



631 



Heine — Continued 

boilers, 
baffling, 27 
circulation, 19, 568 
cleanmg, 21 
cross drum, 43 
longitudinal drum, 23 
marine, 47 

overload capacity, 19, 568 
small space required, 31 
water purification in, 19 
by-pass superheater, 78 
marine superheater, 49 
service, 23 
soot blowers, 31, 41 
superheat control, 29, 78 
superheaters, 29, 78 
Heine reinforced concrete chimney, 209 
Hetnpel gas analysis apparatus, 535 
Henderer tube expander, 613 
High 
draft loss, waste heat boilers, 142 
gas velocity heat transfer, 385 
heat value of fuels, 485 
pressure feed pumps, 301 
setting 
anthracite, 96 
smokelessness, 91 
vertical baffling, 91 
water signal, 551 
Hog wood 
firing, 566 

fuel bed thickness, 566 
Hopper ashpits, 109 
Horizontal baffling, 61 
flame travel and, 93 
furnace temperature and, 87 
smoke and, 87, 93 
Horsepower, boiler, 55 
Hot water and feed pump 
capacity, 299, 317 
corrosion, 301 
suction lift. 317 
Huddling chamber, safety valves, 554 
Humidity of air, 
heat loss due to, 545 
observing. 536 
tables, 537 
Hydrocarbons, heat loss due to, 546 
Hydrogen, 
combustion data, 393 
in fuels, 453 

heat loss due to, 543 
specific heat, 404 



Ice plants, feed water heaters for, 329 

Idle boilers, care of, 613 

Ignition temperatures, 391, 394 

Illinois stoker, 169 

Impact pressure, pitot tube, 233 



Induced draft, 236 

chimney connection, 241 

cinder separating fan, 237, 572 

dampers, 241 

density of gases, 239 

diagram, 225 

dirt unbalancing fans, 236 

erosion of fans, 236 

fan speeds, 237 

sizes of fans, 237 

weights of fans, 237 
Infusorial earth (Kieselguhr), 357 
Injectors, 319 

'"breaking," 323 

exhaust steam, 323 

inspirators, 322 

live steam, 319 

scale in, 2)2?) 

steam pressure range, 321 

suction lift. 321 

suction piping, 323 

superheated steam, 321 

thermal efficiency, 323 
Inleakage of air, 

see Air, leakage in settings, 
Inspection of boilers, 614 

precautions, 615 

report, 616 
Inspirators, 322 
Instrument boards, 584 
Insulating brick, 155 
Isothermal expansion, 407, 414 



Jet blowers. 227 

Jones stoker, 162 

Junker gas calorimeter, 482 

K 

Kellog chimneys, 203 
Kent chimney table, 176 
Ivey handhole caps, 27, 47, 54 
Kieselguhr, 357 
Kirkivood gas burner, 128 
Kling-Weidlein gas burner, 130 
Koerting oil burner, 123 
oil burning system, 123 



Laclede-Christy stoker, 170, 566 
Ladders, 

brick chimneys, 206 

steel chimneys, 195 
Lance, steam, 43 
Laning, or stratification, 93 
Larry, coal weighing. 602 
Lea-'Courtenay centrifugal feed pump, 

307 
Liberating surface, steam, 67 
Lightning rods, 206 



632 



INDEX 



Lignite. 436 

briquets, 471 

composition, 436 

tiring. 566 

forced draft. 566 

fuel bed thickness. 566 

heat value, 436 

moisture in. 436 

weight of. 466 
Lining, 

air-cooled furnace. 151 

brick chimneys, 205 

steel chimneys, 195 
Liptak flat arch, 153 
Liquid fuels. 478 

boiler tests. 550 
Load 

dispatching. 569 

signals, 569 
Lopulco powdered coal burner. 116 

feeder, 115 
Low 

heat value of fuels, 4S5 

water signal 551 
Lubrication and superheat, 75 

M 

Marine 
boilers 

corrosion. 49 
Heine, 47 
settings. 143 
zinc plates in. 49 
superheaters. 49 
Masoti damper regulator, 5S3 
Mechanical 
draft. 223 

equivalent of heat, 378 
stokers. 159 
chain grate. 167 
front feed. 159 
hand operated, 171 
overfeed, 159 
settings. 100 
side feed, 1 59 
underfeed, 161 
treatment of water, 505 
Megass. see Bagasse 
Mercurv thermometers. 373 
Meters.' 

Bailey boiler. 598 
coal, helical vane, 602 
steam flow. 595 

variable orifice. 597 
water. SS7 
boiler testing. 516 
classification. SS7 
gravimetric. 589 
Venturi cppacities, 593 
Venturi diagram. 590 
^^enturi formula. 591 
V-notch. 589 



Meters — Continued 
water — Continued 

V-notch formula. 591 
volumetric. 589 
Model stoker, 161 
^Moisture in 
air, 536, 545 
coal. 450. 517 
errors. 547 
fuels, see fuel in question 

loss due to, 477, 542 
steam. 518 

factor for. ^28 
Molecular weights. 391 
MoUier diagram. 416 
Moloch stoker. 162 
Mono COo recorder. 578 
Mortar, 

firebrick, 147 
fluxes in, 151 
fusion of. 151 
weight of fireclay. 151 
Muck's coal classification, 437 
Mud drum, internal. 35. 45 

N 

Xapicr, flow of steam, 421 
Xational stoker, 171 
Natural gas 

burners. 128 

burning. 127 

composition. 483 

heat value, 483 

working pressure, 482 
Xa^"A- oil specifi.cations. 497 
Nitrogen 

in coal. 453 

specific heat. 403 
Nozzles, steam, 417 

convergent. 419 

expansion. 417 

P,>0.58P,. 421 

Rateau, 420 

O 

Oil. 

atomizing. 119 
burners. 119 

location, 119 
burning. 117 

boiler tests, 550 

chimney table. 190 

chimnevs. 189 

combustion chamber. 117 

nre brick surface. 117 

furnace design. 119 
consumption, stand-by boilers. 568 
crude. 479 
fuel. 478 

composition. 479 

handling. 610 



INDEX 



633 



Oil — Continued 
fuel — Continued 

heat value, 479 
settings, 117 
specifications, 497 
specific gravity, 479 

composition, 483 

heat value. 483 
heater, 124 

and pump, 124 
separation in 

feed water heaters, 326 

Heine boilers, 45 
separators, 293 
tar. 

composition. 481 

heat value, 481 
-tar, 481 
Operating- 
cost of feed pumps, 305 
cost of steam generation, 617 
economical boiler. 584 
under ''test conditions," 585 
waste heat boilers, 142 
Optical pyrometer, 2)77 
Orifice, steam flow. 421 
Orsat apparatus, 532 
operation. 533 
solutions, 533 
Oxygen 

in coal, 453 
specific heat, 403 

P 

Pattersoii-Berrxman feed water heater, 

327 
Peabody 

calorimeter, 518 
entropy diagram, 415 
Peat, 435 
briquets, ^71 
lieat value. 436 
weight, 466 
Peck pivoted bucket conveyor, 606 
Pipe 
ancliors. 286 
])rass, 252, 260 
bursting pressure, 257 
capacity, 

double extra heavy. 256 
extra heavy, 255 
standard, 253 
cast iron, 251 

condensation and superheating. 69 
copper. 252. 260 
extra heavy 
brass, 261 
copper. 261 
iron, 255 
lieat efi^ect on strength of, 252 
fittings, 
brass, 263 



Pipe — Continued 
fittings — Continued 

cast iron, 261 

cast steel, 261 

flange, 263 

flange unions, 267 

flanged, 125 lb., 265 

flanged, 250 lb., 268 

general, 261 

malleable iron, 261 

names of, 264 

nut unions, 265 
flanges, 

125 lb., 267 

250 lb., 269 

materials, 271 
hangers, 293 
headers, cast steel, 252 
insulation, 360 
sizes, 

double extra heavy, 256 

extra heavv, 255 

large O. D.. 257 

standard, 253 

steam, saturated, 276 

steam, superheated, 281 

water, 281 
strength of, 257 
supports, 293 
water, 260 
weight, 

brass, 260 

copper, 260 

double extra heavy, 256 

extra heavy, 255 

large O. D., 257 

standard, 253 
Pipes, 
flow of 

steam in, 275 

water in, 281 
friction pressure drop, 275 
steam, 

size charts. 277 

velocity-, 275 
velocit}', 

steam, 275 

water, 283 
Piping, 
blow-off, 275 
boiler water gage, 551 
color identification, 251 
design. 243 
diagram. 251 
drainage of steam, 243 
expansion 

and contraction, 283 

l)ends. 287 

force, 286 

joints, 286 

of materials, 285 



634 



INDEX 



Piping — Continued 
feed pump suction, 318 
flange joints, 267 
identification. 251 
insulation, 360 
materials. 

expansion of, 285 

moduli of elasticity, ^^6 
saturated steam, 259 
screwed flanges. 268 
slope of steam, 243 
steam, draining, 243 
superheated steam, 69, 83, 259 
system. 

duplicate header. 245 

loop header, 247 

ring header. 247 

selection. 244 

single header. 244 

unit, 247 

unit, modified. 249 
Van Stone joint, 271 
vibration in steam. 243 
water in steam, 243 
water hammer in steam, 243 
welded flanges, 271 
wrought iron, 251 

Pitot tube. 232 
double, 233 
water meter. 591 

Plastic 
rirebrick, 152 
fireclaj- cements. 151 

Plasticity- of firebrick, IAS 
Playford stoker. 170 
Folakoz' control board, 585 
Powdered coal 
burners, 116 
burning. Ill 

control of air, 116 
equipment 113 
feeders, 115 
settings. 111 
Power feed pumps. 309 
Pneumatic convevors, 
ash, 608 

wood refuse, 133 
Precision Instrument Co., draft gage. 581 
Pressure, 
effect on boiling point of water, 500 
effect on gases. 398 
excess feed water, 297 
gages, 

boiler testing, 518 

correcting, 557 

description, 555 

head of water in pipes, 556 

location, 556 

siphons, 556 



Pressure — Continued 
gages — Continued 
tester, 557 
vibration. S57 
water seal, 5S6 
regulators, 
excess feed, 310 
feed pump. 310 
Priming, 67 

bad feed water and, 510 
Processes, industrial 
air heated by, 341 
superheated steam for, S3 
waste heat from, 139 
Producer gas, 
burning. 131 
composition of, 483 
heat value, 483 
Properties of 
gases, 398 

saturated steam, 424 
superheated steam, 429 
water, 499 
Prosser tube expander, 613 
Proximate analysis of coal, 451 
Ps3-chrometric tables. 537 
Pulverized coal, see Powdered coal 
Pumps, see Feed pumps 
P\Tometers, 
accuracy-, 371 
calibrating, 370 
electrical resistance. 373 
mechanical, 374 
optical, 377 
radiation, 377 
range of, 371 
thermo-electric. 373 



Quick steaming from banked fires, 568 
Quiglcy powdered coal burner, 116 

R 

Radial brick chimneys, 201 
Radiation. 379 

boiler settings, 153 

heat loss. 546 

oil burning, surface. 117 

pyrometers. 377 

Stefan's formula, 379 

surface for oil burning, 117 
Rankine's convection formula, 385 
Rateau, flow of steam, 420 
Rated H.P. of boilers, 55 
Ray rotar>- oil burner, 124 
Reaumur temperature scale, 370 
Reboilers for ice plants, 329 
Receiver steam separators, 295 
Recorders, 

CO,, 577 



INDEX 



635 



Recorders — Continued 

smoke, 550 
Refuse 

burning settings, 133 

composition of municipal, 191 

destructor chimneys, 191 
Refractories, 148 

perforated blocks, 151 

thermal conductivity, 155 

weights of, 151 
Regulators, 

draft, 584 

excess feed pressure, 310 

feed pump pressure, 310 

feed water, 313 

superheat temperature, 78 
Reinforced concrete chimneys, 207 
Reinforcing old brick chimneys, 213 
Renewing boiler tubes, 43, 613 
Republic flow meter, 594 
Resistance, 

heat, 385 

surface, to heat flow, 347 
Richardson coal scale, 601 
Riley stoker, 165 
Ringelmann smoke chart, 549 
Roach stoker, 162 
Roney stoker, 161 
Ross expansion joint, 290 
Rust concrete chimney, 211 

S 

Safety valves, 

A.S.M.E. Code, 551 

blow down 
allowed, 553 
control, 554 

discharge piping from, 243 

huddling chamber, 554 

operation of pop, 554 

pressure rise allowed, 551 

size chart, 272 

specifications, 271 

superheaters, 75, 555 
Sampling- 
coal, 445 
boiler testing, 517 
errors, 547 

flue gases, 531 
tubes, for, 531 
Sand, fire, 151 
Sanford Riley stoker, 165 
Sawdust 

burning, 566 

fuel bed thickness, 566 

grate bars, 99 

heat value, 473 
Scale, boiler 

formation, 511 

heat transfer, 511 



Scale, boiler — Continued 

injector, 323 

removal, 611 

superheaters, 76 
Scales, 

temperature, 370 
conversion, 370 
thermodynamic, 370 

weighing, 

boiler testing, 517 
continuous, 599 
conveyor, 599 
track, 599 
Secondary air admission, 90 
Sedimentation tanks, 508 
Seger cones, 377 
Semi-anthracite coal, 436 
Semi-bituminous coal, 436 
Separating calorimeter, 522 
Separator, feed water oil, 326 
Settings, see Boiler settings 
Shavings, 

burning, 133, 566 

burning dry, 134 

grate bars, 99 

heat value, 473 
Signals, 

high water, 551 

load, 569 

low water, 551 
Smoke, 

baffling, 65, 93 

causes, 571 

combustion space, 571 

curtain walls, 93 

deflection arch, 93 

down draft furnace, 95, 100 

furnace 
design, 571 
temperature, 571 
volume, 85 

gas passage areas, 93 

height of furnace chamber, 90 

horizontal baffling, 62, 87, 93 

indicators, 550 

observations, 548 

ordinances, 571 

overloads, 571 

prevention, 569 

recorders, 550 

records, 65 

reports, 548 

RingeUnann chart, 549 

tile furnace roof, 87 

vertical baffling, 93 
Soft coal, see Coal, bituminous 
Soot 

blowers, 610 
baffles and, 65 
boilers, 39, 41 



636 



IXDEX 



Soot — Continoed 
blowers — Continued 
eccHioniizer, 333 
superheater, 31 
collectors in chimneys, 207. 208 
heat loss by formation of, 547 
Sorge-Cochrane water softener. 509 
Specific heat, 378 

r : -;» 

r :t _ ; ations. 
j>oiler, standard, 49 
coat 486 
oil fueL 497 
Xavy, 497 
railroad, 498 
Spontaneous combustion of coal, 467 
Stadcs, see Chimnejrs 
Staples and Pfeifer oil burner, 120 
Stand-by boilers, 568 
fire protection, 568 
oil consunqytion, 568 
quick steaming, 568 
Static pressure, pitot tube, 232 
Steam 
calorimeters. 
Carpenter, 522 
connections, 523 
fommla, 521 
Pcabody. 518 
separating. 522 
throttling, 518 
consumption, 
auxiliaries, 423, 547 
feed pumps, 302, 305 
cost 
accounts, 616 

Polakoz' method of reducing. 585 
diagram 
M oilier, 416 
Peabody, 415 
disengaging surface, 67 
entropy, 407 

diagrams. 415. 416 
factor for moisture in, 528 

.-. -21 
meters. 595 

meters, %-ariable orifice, 597 
Xapier. 421 
nozzles, 421 
pipes, 275 
Ratcau. 420 
generation, 
maintenance costs. 618 
operating costs, 617 
reducing cost of. 587 



Str ~ — 



rs. 608 



erers. 595 



--t» 



^^ram, 415 



re drop. 275 



275 



see Piping systems 



'" =^^c^^. see Pressure gages 

5 ol410 
r -ated, 424 
- t ^ ;triieated, 429 
quilir*. 51S 
receiver; 2^' 



35,43 



i*^ steam 



SQiar; 

separ^.i.r, _- 

superheated, -t 

superheater?, ^t 

tables, 
saturated, 424 
superiieated. 429 
Steel chimneys, see Chimneys, steel 
Stefan's radiation formula, 379 
Stevens stoker, 163 
Stokers. 159 

see ^'Tecnanica! stokers. 

; ~ " ' \ _ - ^ • 

- ' " — ; oaL see Coal storage 

- i or laning, 93 



5!tion, 474 

t. 474 



lerials and heat 97. 239. 



Sub-bituminous coal. 436 

^ : ; lift 

izr.Ds. 317 

-. ::. 317 



s. 318 



I N D E X 



637 



Sudden loads from banked fires, 568 
Sulphur 

combustion data, 393 

in coal, 451 

in U. S. coal, 463 
Superheat, 

accurate control, ll 

boiler load and, 75 

control of, 75 

damage by tiuctuation of, 75 

fluctuations, 75 

regulation, 75 

regulator, 78 

variation with 

furnace temperature, 76 
gas flow, 76 
load, 76 
steam flow, 76 

weakening materials. 83 
Superheated steam, 69 

advantages, 69 

automatic temperature control, 78 

lioiler eff^iciency, 69 

constant temperature. 11 , 1'^ 

Corliss engines and. IZ 

cylinder condensation and, 69, 72 

danger of temperature fluctuations, 75 

economy, 69 

engines using, tests of, 72 

erosion of turbine blades. 73 

European practice, IZ 

extra fuel for, 69 

fittings, 83 

flue gas temperature and, 69 

industrial uses of, 83 

injectors and, 321 

limit of economy with engines, 71 

lubrication and, 75 

pipe condensation and, 69 

pipe sizes, 281 

piping, 259 

poppet-valve engines and, 75 

reciprocating engines and, 71 

slide-valve engines and, IZ 

tables, 429 

taking temperature, 523 

temperature-entropy diagram, 69 

tests of engines using, 11 

theoretical engine and, 1'}) 

turbines and, IZ 

blade erosion of, 12) 

variation of temperature, 75 

velocities in piping, 69, 83 

water gas producers and, 83 
Superheated vapors, 411 
Superheaters, 69 

attached, 75 

burning, 76 

liy-pass, 77 



Superheaters — Continued 
cleaning, 31 
details, 11 
drains, l(i 
flooding, l(i 
heat transfer rate. 81 
Heme, 29. 34. 11 
marine, 49 
materials, 83 

weakness of, 83 
position of, 76 
protecting, 76 
requirements, 79 
safety valves, 75, 555 
scale in, 16 
separately fired, 75 
soot blower. 31 
surface 

efticienc3\ 69 

required. 79 
types of, 75 
Surface, 
grate, 57 
heating, 

boilers, 57, 562, 567 

cost of boilers by. 57 

economizer, 337 

efficiency of superheater. 69 

gas temperature drop and. 387 

superheater. 79 
resistance of insulation. 360 

to heat flow, 347 
steam disengaging, 67 
waste of coal with bare hot, 349 

T 

Tan bark 
Ixirning, 133 
composition, 475 
firing, 567 

fuel bed thickness. 567 
grate bars, 99 

heating surface ratio with. 567 
heat value, 474 
moisture in, 474 
settings for burning. 133 
Tar 

burners, 125 
burning, 125 
composition 

coal, 481 

oil, 481 
heat value 

coal, 481 

oil, 481 
-oil. 481 

specific gravity, 481 
weight of coal, 481 
Taylor stoker. 164 



638 



I X D E X 



Temperature 

absolute, 370 

absolute zero of. 370 

color schedule. 377 

-entropy diagram, 415, 416 

fixed points, 371 

scales, 370 

conversion, 370 
thermodjTiamic. 370 
Testing boilers, see Boiler testing 
Thermal units, 378 

Thermod3-namic temperature scale, 370 
Thermo-electric pyrometers, 373 
Thermometers. 

accuracy. 371 

alcohol, 373 

calibration. 370, 373 

mercur\-. 373 

range of, 371 

stem correction, 373 

vapor, 377 

wells, 373 
Thermometn-. 369 
Tile 

baffles. 66 

furnace roof and smoke. 87 

roof and furnace temperature, S7 
Tolerance in guarantee tests. 547 
Treatment of water, see Water 
Trenches, insulating piping in. 367 
Trials of boilers, see Boiler testing 
Triplex feed pumps. 309 
Tubes 

beading. 613 

cleaning boiler, 43 

cleaners. 

hammer type. 611 
turbine t\-pe. 611 

conductivity of boiler, 383 

expanders. 613 

flaring. 613 

pitot, 232 

renewing boiler, 43, 613 

rolling. 613 
Tunnels, insulating piping in, 367 
Tupper grate bars, 97 
Turbines, 

auxilian.-. 341 

blades, erosion, 73 

boiler feed pumps and. 345 

fans and. 227. 343 

feed pumps and, 345 

superheated steam and. 73 

tube cleaners, 611 

U 

Ultimate analysis of coal, 451 
Underfeed stokers. 161 
Units, 
British thermal, 378 



Units — Continued 

heat, 378 

work, 378 
Universal stoker. 163 



Vacuum reboilers. 329 
Valves, 

ashpit. 111 

automatic non-return. 274 

blow-off. 274. 560 

check, 274 

gate, 273 

globe, 273 

safety-, 271, 551 

safet}-, superheater, 75, 555 
Vapor 

thermometers, 377 

water 

specific heat, 405 
weight of air and, 401 
Vapors, characteristics of, 409 
\'elocit3', 

era 5 

chimneys, 189 
draft loss altering. 187 
draft loss generating. 187 
heat transfer and. 385 
waste heat boilers, 141 
pressure, pitot tube, 233 
steam, 
nozzles. 417 
pipes. 275 
superheated. 69, S3 
water, pipes, 283 
Venturi 

chimneys, 191 
meter, 

capacities. 593 
diagram, 590 
formula. 591 
Vertical baffling, 61 
extinguishing action. 93 
head room for, 91 
smoke and. 93 
Vibration in piping. 243 
Vitrified brick, 156 
V-notch meter, 589 

formula, 591 
Volatile matter in coal. 451 

W 
Walls, 
air space in boiler, 145 
boiler setting, 145 
insulation of boiler. 153, 367 
leakage through setting, 157, 577 
smoke and curtain. 93 
ties for setting. 155 



INDEX 



639 



Washing coal, 458 
Waste heat boilers, 139 
airtight settings, 142 
baffling, 141 
dust in, 142 
heat transfer, 141 
high draft loss, 142 
high gas velocity, 141 
industrial furnaces, 141 
operation, 142 
Waste of coal with bare hot surfaces, 349 
Water 
acidity, 503 

air in, removal of, 329 
alkalinit}', 503 

test, 505 
analyses, table of, 504 
analysis, 503 

boiling point and pressure, 500 
causticity, 503 

test, 505 
characteristics of boiler feed, 501 
chemical treatment, 507 
classification of feed, 505 
concentration test of feed, 505 
corrosion, 510 

gases in, 503 
foaming with bad, 510 
-gas, 

composition, 483 

generators and superheated steam. 83 

heat value of, 483 

tar burning, 125 
gases in feed, 503 
grate, 95, 100 
hardness,. 

factors, 504 

permanent, 501 

temporary, 501 

test, 503 
heaters, see Feed water heaters 
heat treatment of, 507 
impurities in, 501 
meters, see Meters, water 
permanent hardness, 501 
piping, 260 

flow in, 281 

insulating cold, 367 

sizes of, 281 

velocity in, 283 
priming and bad. 510 
properties of, 499 

purification in Heine boilers, 19. 35, 45 
softening, see Water treatment 
solid matter in, 503 



Water — Continued 
specific heat of, 499 
temporary hardness, 501 
thermal treatment, 507 
treatment, 

boiler compounds, 510 
chemical feed, 507 
chemical proportioners, 50S 
filters, 508 
hot process, 508 
Heine mud drum and, 35, 45 
mechanical, 505 
sedimentation tanks, 508 
Sorge-Cochrane, 509 
Zeolite, 508 
vapor, 

characteristics, 409 
specific heat, 405 
• ^yeight of air and, 401 
weight, 

maximum density, 499 
volume and, 499 
Weir, formula for V-notch, 591 
Westinghoiisc-Roney stoker, 161 

underfeed stoker, 164 
Wet fuels, heat value of, 477 
JVetsel stoker, 161 
JVeiderholt chimneys, 211 
Wind, 

heat insulation and, 361 
pressure on chimneys, 193 
IVitt oil heater and pump, 124 
Wood fuel, 435, 473 
chimneys, 191 
chips, 134 

coal and, 134 
composition, 473 
cord, 566 

fuel bed thickness, 566 
grate bars, 99 
heat value, 435, 473 
hog, 566 

refuse settings, 133 
sawdust, 566 
slab, 566 
Work, unit of, 378 
WorthiiigtO}i water weigher, 589 



Yarzvay blow-off valve, 560 



Zeolite water treatment, 508 
Zero of temperature, absolute, 370 
Zinc plates in marine boilers. 49 



T^lBUHC ,/«). new- ^ 



PRESS OF 

KUTTERER-JANSEN PRINTING CO. 

ST. LOUIS 






-? ^ 



.-^ 



-/> .s^Vv'^' 



o^' 



